Deck 30: How Animals Move

Question 1

If you inflate a balloon and then let it go, the air rushing out moves the balloon in a way that is similar to the way that a ________ moves.

A) snake
B) kangaroo
C) squid
D) shark

Answer 1

C

Question 2

Which structure constitutes part of the axial skeleton?

A) skull
B) pelvic girdle
C) pectoral girdle
D) radius

Answer 2

A

Question 3

An important function of the bones in the skeleton is to

A) provide a source of ATP.
B) generate hormones.
C) add weight.
D) support the body.

Answer 3

D

Question 4

The way the tendons in the legs of a kangaroo aid in locomotion is most like

A) stepping in mud and the mud spreading out as your foot sinks in.
B) stretching and contracting a rubber band.
C) the circular movements of the wheels of an automobile.
D) smashing an apple to make applesauce.

Question 5

Which statement about hydrostatic skeletons is true?

A) Hydrostatic skeletons are nonflexible.
B) Hydrostatic skeletons provide little support for muscle action.
C) Hydrostatic skeletons produce rigid animals that maintain one shape.
D) Hydrostatic skeletons can protect internal organs.

Question 6

Which animal has an endoskeleton made entirely of cartilage and reinforced with cartilage?

A) bullfrog
B) mackerel
C) shark
D) robin

Question 7

Why is a newly molted crab unusually slow and clumsy?

A) Its new exoskeleton cannot support the forces that its muscles generate.
B) It temporarily lacks an exoskeleton.
C) Its muscles are still forming their connections with the new exoskeleton.
D) Its neurons are still forming their connections with the new muscles.

Question 8

Which is most like an exoskeleton?

A) springs in a mattress
B) a water balloon
C) a suit of armor
D) the hair covering the surface of a bear

Question 9

Which statement about locomotion is true?

A) Locomotion requires energy to overcome friction and gravity.
B) Gravity is a greater locomotion problem for animals in water than for those on land.
C) Overcoming friction is a greater locomotion problem for land animals than for those that live in water.
D) Bone strength is more important than body shape in the locomotion of land animals.

Question 10

Which provides a base of support for the bones of the forelimbs and hind limbs to the axial skeleton in a human?

A) pectoral girdle
B) pelvic girdle
C) cervical vertebrae
D) appendicular skeleton

Question 11

Which object is most like a hydrostatic skeleton?

A) a water balloon
B) a hot-air balloon
C) a piece of M&M candy
D) a bowling ball

Question 12

Which animal has an exoskeleton?

A) human
B) trout
C) shark
D) clam

Question 13

Vertebrae are differentiated during embryonic development by the

A) amount of spongy bone present.
B) length of the backbone.
C) degree of structural support needed.
D) pattern of homeotic gene expression.

Question 14

The evolution of the vertebrate skeleton system

A) originated from a snake-like animal with limbs.
B) enabled tetrapods to colonize land.
C) made animals significantly taller.

Question 15

Earthworms have a(n)

A) exoskeleton.
B) endoskeleton.
C) hydrostatic skeleton.

Question 16

An airfoil provides lift because air moving over a wing must travel

A) a greater distance than air moving under the wing, creating a lower pressure system above the wing.
B) a greater distance than air moving under the wing, creating a higher pressure system above the wing.
C) a lesser distance than air moving under the wing, creating a lower pressure system above the wing.
D) a lesser distance than air moving under the wing, creating a higher pressure system above the wing.

Question 17

Earthworms crawl by

A) undulating from side to side.
B) peristalsis.
C) extending their belly scales.
D) pushing themselves forward from the tail.

Question 18

You are cleaning out an old lab freezer and find a tube that contains the ground-up remains of an unknown animal. Your research advisor suggests that you perform chemical assays to determine what molecules made up the animal. After analyzing the data, you determine that the animal contained a large amount of chitin. What type of animal was in the tube?

A) mollusc
B) reptile
C) arthropod

Question 19

A racehorse cannot stand on one leg, but when it runs it rarely has more than one leg on the ground. Why is a running horse more stable than a standing one?

A) Its legs tilt so the hooves fall in line with its center of gravity.
B) Its momentum gives it stability.
C) It uses its neck for balance the way a tightrope walker uses a pole.

Question 20

Suppose that the circular muscles in an earthworm have become selectively paralyzed such that they are not able to contract. How will this affect the earthworm's locomotion?

A) The earthworm will be able to elongate, but not get thicker.
B) The earthworm will be able to get thicker, but not elongate.
C) The earthworm will not be able to elongate or get thicker.
D) The earthworm will be able to crawl as normal.

Question 21

A thick filament consists of

A) actin molecules.
B) myosin molecules.
C) actin and myosin molecules.

Question 22

Bone is composed of

A) living cells that secrete a surrounding matrix.
B) a hard composite of phosphate and sodium ions.
C) channels containing lymphoid tissue.
D) hardened cartilage.

Question 23

Functionally, the muscle fiber's fundamental unit of contraction is the

A) thick filament.
B) myofibril.
C) sarcomere.
D) Z line.

Question 24

Osteoporosis is characterized by

A) hairline cracks in long bones, such as the femur.
B) low bone mass and structural deterioration of bone tissue.
C) low phosphate levels in bone.
D) lack of vitamin E in bone tissue.

Question 25

Which part of a bone contains mostly stored fat?

A) red bone marrow
B) fibrous connective tissue
C) spongy bone
D) yellow bone marrow

Question 26

Skeletal muscles

A) are found in and around internal organs.
B) get longer when they contract.
C) work in antagonistic pairs.
D) push on bones to make them move.

Question 27

Which list of muscle components is in the correct order from smallest to largest?

A) muscle, sarcomeres, myofibrils, muscle fibers
B) sarcomeres, myofibrils, muscle fibers, muscle
C) sarcomeres, myofibrils, muscle, muscle fibers
D) myofibrils, muscle, sarcomeres, muscle fibers

Question 28

Muscles are connected to bones by

A) cartilage.
B) ligaments.
C) tendons.
D) myofibrils.

Question 29

To treat a broken bone, physicians will

A) graft new bone to the region.
B) exercise the area of the broken bone.
C) prescribe bed rest and calcium supplements.
D) reshape broken bone parts to their natural position.

Question 30

Structurally, a sarcomere is

A) the region between two thick filaments.
B) the region between two Z lines.
C) an array of Z units.
D) the region between a thick filament and the next thin filament.

Question 31

The shoulder joint where the humerus meets the pectoral girdle is an example of a

A) hinge joint.
B) ligament.
C) pivot joint.
D) ball-and-socket joint.

Question 32

Which part of a bone contains red bone marrow?

A) compact bone
B) fibrous connective tissue
C) spongy bone
D) yellow bone marrow

Question 33

During muscle contraction,

A) only the thin filaments shorten.
B) only the sarcomere shortens.
C) only the thick filaments shorten.
D) both the thick filaments and the sarcomere shorten.

Question 34

Which statement about skeletal muscle fibers is true?

A) Each muscle fiber is composed of many cells.
B) Each muscle fiber is composed of globular proteins.
C) Each muscle fiber contains one sarcomere.
D) Each muscle fiber contains actin and myosin.

Question 35

Which statement best describes the molecular basis of muscle shortening?

A) Individual filamentous proteins contract.
B) Individual filamentous proteins shorten by coiling.
C) Rod-shaped protein polymers shorten by losing subunits from their ends.
D) Protein filaments ratchet along other protein filaments.

Question 36

Osteoporosis has long been recognized as a problem for women after menopause, but it is also emerging as a health concern for

A) women and men ages 20-30.
B) women ages 16-18.
C) men over the age of 65.
D) men and younger people in general.

Question 37

If you lay your forearm along a table, you can rotate it so that your hand changes from a palm-down to a palm-up position. This is possible because your radius and ulna join at a

A) ball-and-socket joint.
B) hinge joint.
C) pivot joint.
D) ligament.

Question 38

One change that occurs within a sarcomere during muscle contraction is that the

A) thin filaments get thicker.
B) thick filaments move closer together.
C) Z lines move closer together.
D) thick filaments get thicker.

Question 39

According to the sliding filament model of muscle contraction, a sarcomere contracts when its

A) thick filaments slide across its Z lines.
B) thin filaments slide across its Z lines.
C) thin filaments slide along its thick filaments.
D) thick filaments move closer together.

Question 40

Thin sheets of ________ form a cushion-like surface for moving joints

A) red bone marrow.
B) cartilage.
C) spongy bone.
D) compact bone.

Question 41

Which part of this figure depicts the thoracic vertebrae?

A) part A
B) part B
C) part C
D) part D

Question 42

Which muscle(s) would have the greatest number of muscle cells per motor unit?

A) muscles controlling the movement of our hands
B) facial muscles
C) a thigh muscle
D) muscles controlling the movement of an eyeball

Question 43

Which of the following statements best describes the power stroke of muscle contraction?

A) The myosin head bends, pulling the thick filament toward the center of the sarcomere.
B) The myosin head bends, pulling the thin filament toward the center of the sarcomere.
C) The actin head bends, pulling the thin filament toward the center of the sarcomere.
D) The actin head bends, pulling the thick filament toward the center of the sarcomere.

Question 44

Muscles that are constantly active, such as those maintaining our body posture, have a high proportion of

A) fast, fatigue-resistant fibers.
B) fast, fatigue-susceptible fibers.
C) slow, fatigue-resistant fibers.
D) slow, fatigue-susceptible fibers.

Question 45

A motor unit is

A) the bundle of axons that goes from the spinal cord to a muscle.
B) one of the connective tissue-wrapped bundles of muscle fibers in a muscle.
C) a motor neuron and all of the muscle fibers it controls.
D) the muscle or group of muscles that accomplishes a specific movement.

Question 46

Your friend is complaining of back pain. She also says that she hurts the most near her neck. What part of her back may have been injured?

A) cervical vertebrae
B) thoracic vertebrae
C) sacrum
D) coccyx

Question 47

The calcium that triggers muscle contraction is stored in the

A) motor neuron.
B) plasma membrane of cells.
C) endoplasmic reticulum.
D) mitochondria.

Question 48

A tennis player serving the ball uses fast muscle fibers. The ATP needed to accomplish this comes from

A) anaerobic fermentation.
B) aerobic respiration.
C) conversion of lactic acid to ATP.
D) conversion of Ca2+ to ATP.

Question 49

Which statement regarding exercise is true?

A) Most of the ATP for aerobic exercise comes from aerobic respiration.
B) During a short burst of activity such as a sprint, the main source of energy is aerobic respiration.
C) If the demand for ATP outstrips oxygen supply, muscles switch to aerobic fermentation.

Question 50

Fast muscle fibers contain a high proportion of myofibrils, which allows the fibers to generate high amounts of force. However, this leaves little room in the fibers for other cellular components, including mitochondria. The opposite is true for slow muscle fibers. Does this information support or refute what you know about the fatigue-susceptibility of fast and slow fibers? Why or why not?

A) It supports it because if fast fibers have less room for mitochondria than slow fibers do, they cannot produce as much ATP and thus are less fatigue-resistant than slow fibers.
B) It supports it because if fast fibers have less room for mitochondria than slow fibers do, they can produce more ATP than slow fibers and thus are more fatigue-resistant than slow fibers.
C) It refutes it because if fast fibers have less room for mitochondria than slow fibers do, they can produce more ATP than slow fibers and thus are less fatigue-resistant than slow fibers.
D) It refutes it because if fast fibers have less room for mitochondria than slow fibers do, they cannot produce as much ATP and thus are more fatigue-resistant than slow fibers.

Question 51

The role of calcium in muscle contraction is to

A) release ADP and phosphate from myosin.
B) make it possible for ATP to bind to actin.
C) make it possible for myosin to bind to actin.
D) make it possible for ATP to bind to myosin.

Question 52

A muscle fiber from the latissimus dorsi (one of the back muscles) of a chimpanzee has a lot of mitochondria and myoglobin and can generate relatively little force. Which type of muscle fiber is being described?

A) a fast, fatigue-resistant fiber
B) a fast, fatigue-susceptible fiber
C) a slow, fatigue-resistant fiber
D) a slow, fatigue-susceptible fiber

Question 53

Which part of this figure depicting a bone shows spongy bone tissue?

A) part A
B) part B
C) part C
D) part D

Question 54

The sequence of events that cause a sarcomere to contract can be summed up in the correct order as

A) detach, extend, contract, attach.
B) attach, pull, extend, contract.
C) detach, extend, attach, pull.
D) attach, contract, detach, recoil.

Question 55

After reading the paragraphs below, answer the questions that follow.
Rickets is a softening of the bones that can lead to frequent fractures and skeletal deformities. The legs of a person with rickets tend to bow outward under the force exerted by body weight and movement. British scientists found a serious increase in the incidence of rickets and other bone deficiencies among women in Middle Eastern countries who cover their bodies completely to express a form of religious belief, as well as among their breast-fed children.
Most of the body's vitamin D, which is necessary for calcium absorption by bone tissue, is obtained through sunlight acting on the skin. Doctors warn that women who completely cover their skin do not get enough sunlight to produce the vitamin D necessary for bone health. This lack of sun exposure also lowers the level of vitamin D in their breast milk, which means that their children may develop the same vitamin D deficiencies. Lack of calcium and phosphorous, which are needed for bone repair and replacement, can also lead to rickets. Rickets caused by a dietary lack of these minerals is more common in developing countries because dairy products and green vegetables, the best sources of calcium, are not commonly eaten.
As a physician caring for a nursing woman who has chosen to dress in a way that covers her skin but who is concerned about rickets developing in her baby, you might advise her to

A) exercise more.
B) eats lots of meat and potatoes.
C) take vitamin D and calcium supplements.
D) give up smoking.

Question 56

Mutations in the gene for troponin can result in the production of the troponin protein, which has varying affinities for Ca2+ ions. Suppose that in a muscle cell a mutant troponin is expressed that has such a high affinity for Ca2+ ions that once they bind to troponin they cannot unbind. What will likely happen in this muscle cell?

A) Myosin heads will not bind to actin after action potentials stop being received.
B) Myosin heads will bind to actin after action potentials stop being received.
C) Tropomyosin will not move to expose myosin binding sites.
D) Cross-bridges will form between myosin and tropomyosin.

Question 57

An animal's locomotor (relates to locomotion) muscle was dissected and the percentages of fast and slow fibers were determined and plotted in the accompanying figure. Which muscle is the likely source for this data?

A) flight muscles of a migratory bird
B) thigh muscles of a marathon runner
C) neck muscles of a chimpanzee
D) jumping muscles of a frog

Question 58

The neurotransmitter found at the synapse between nerves and human skeletal muscle cells is

A) acetylcholine.
B) epinephrine.
C) dopamine.
D) serotonin.

Question 59

Which treatment could possibly help to transform the bone on the right to the bone on the left?

A) wearing long sleeves while out in the sun
B) swimming for 30 minutes a day
C) removing calcium from the diet
D) taking vitamin D supplements

Question 60

Acetylcholine (ACh) is released by motor neurons and binds to receptors on muscle cells to initiate action potentials. Some snake venom contains specific toxins that bind irreversibly to these receptors and block acetylcholine's ability to bind. If an animal is bitten by a snake with these toxins in its venom, what do you predict would happen?

A) The animal's muscle cells would increase production of myoglobin.
B) The animal's muscles would contract uncontrollably.
C) The animal's muscles would not be able to contract.
D) The animal's muscle cells would show shrinkage in mitochondria.

Question 61

After reading the paragraph below, answer the questions that follow.
The "Ironman" is a version of the triathlon, a race that includes three events: swimming, bicycling, and running. In an Ironman, an athlete must swim 2.4 miles, bike 112 miles, and run 26.2 miles, in that order, without a break. The annual Ironman World Championship is held in Hawaii every year. The men's course record was set in 2011 by Australia's Craig Alexander with a time of 8 hours, 18 minutes, and 37 seconds, and the women's course record was set in 2009 by England's Chrissie Wellington with a time of 8 hours, 54 minutes, and 2 seconds.
Which event of the Ironman would likely contribute the most to bone development and growth?

A) swimming
B) bicycling
C) running

Question 62

After reading the paragraph below, answer the questions that follow.
When sarcomeres contract, they generate force (tension). However, the amount of force generated depends on the sarcomere length and the amount of thick and thin filament overlap. Below is a figure that details the force-generating properties of a single sarcomere. This figure was modified from a scientific paper by Al Gordon and colleagues from 1966 and is a classic illustration of the relationship between sarcomere length and force.
What portion of the graph would involve myosin forming cross-bridges and going through power strokes?

A) from A to B
B) from D to B
C) from B to E
D) from A to E

Question 63

After reading the paragraph below, answer the questions that follow.
When sarcomeres contract, they generate force (tension). However, the amount of force generated depends on the sarcomere length and the amount of thick and thin filament overlap. Below is a figure that details the force-generating properties of a single sarcomere. This figure was modified from a scientific paper by Al Gordon and colleagues from 1966 and is a classic illustration of the relationship between sarcomere length and force.
At what point on the graph is the most tension generated?

A) point A
B) point B
C) point C
D) point E

Question 64

In the year 2000, it was estimated that the number of new osteoporotic fractures in men and women ages 50 and older was 9.0 million: 1.6 million were at the hip, 1.7 million were at the forearm, and 1.4 million were from the spine and humerus. Consider the following data and answer the questions that follow.
Estimated Number of Fractures (in Thousands) Worldwide at the Sites Shown in Men and Women in the Year 2000
$\begin{array}{l}\quad\quad\quad\quad\quad\quad\quad\quad\text { Percentage of }\\\begin{array} { l l l l l } \text { Site of Fracture } & \text { Fractures } & \text { Men } & \text { Women } & \text { Total } \\\text { Hip } & 18.2 & 490 & 1,137 & 1,627 \\\text { Forearm } & 18.5 & 332 & 1,328 & 1,660 \\\text { Spine } & 15.8 & 554 & 862 & 1,416 \\\text { Humerus } & 7.9 & 178 & 528 & 706 \\\text { Other sites } & 39.6 & 1,909 & 1,641 & 3,550 \\\text { Total } & 100 & 3,463 & 5,496 & 8,959\end{array}\end{array}$ Source: Adapted from Johnell, O., & Kanis, J.A. (2006). Osteoporosis International, 17(12): 1726. doi:10.1007/s00198-006-0172-4.

-Compare the percentage of fractures in the hip, forearm, spine, and humerus in men and women combined to the percentage of fractures at other sites in men and women combined. What do you conclude?

A) There are about 50% more fractures in the hip, forearm, spine, and humerus in men and women than in fractures at other sites in men and women.
B) There are about 20% more fractures in the hip, forearm, spine, and humerus in men and women than in fractures at other sites in men and women.
C) There are about 10% fewer fractures in the hip, forearm, spine, and humerus in men and women than in fractures at other sites in men and women.
D) There are 100% fewer fractures in the hip, forearm, spine, and humerus in men and women than in fractures at other sites in men and women.

Question 65

In the year 2000, it was estimated that the number of new osteoporotic fractures in men and women ages 50 and older was 9.0 million: 1.6 million were at the hip, 1.7 million were at the forearm, and 1.4 million were from the spine and humerus. Consider the following data and answer the questions that follow.
Estimated Number of Fractures (in Thousands) Worldwide at the Sites Shown in Men and Women in the Year 2000
$\begin{array}{l}\quad\quad\quad\quad\quad\quad\quad\quad\text { Percentage of }\\\begin{array} { l l l l l } \text { Site of Fracture } & \text { Fractures } & \text { Men } & \text { Women } & \text { Total } \\\text { Hip } & 18.2 & 490 & 1,137 & 1,627 \\\text { Forearm } & 18.5 & 332 & 1,328 & 1,660 \\\text { Spine } & 15.8 & 554 & 862 & 1,416 \\\text { Humerus } & 7.9 & 178 & 528 & 706 \\\text { Other sites } & 39.6 & 1,909 & 1,641 & 3,550 \\\text { Total } & 100 & 3,463 & 5,496 & 8,959\end{array}\end{array}$ Source: Adapted from Johnell, O., & Kanis, J.A. (2006). Osteoporosis International, 17(12): 1726. doi:10.1007/s00198-006-0172-4.

-Fractures at sites other than hip, forearm, spine, and humerus were

A) equally common in men than in women.
B) less common in men than in women.
C) more common in men than in women.

Question 66

After reading the paragraph below, answer the questions that follow.
The "Ironman" is a version of the triathlon, a race that includes three events: swimming, bicycling, and running. In an Ironman, an athlete must swim 2.4 miles, bike 112 miles, and run 26.2 miles, in that order, without a break. The annual Ironman World Championship is held in Hawaii every year. The men's course record was set in 2011 by Australia's Craig Alexander with a time of 8 hours, 18 minutes, and 37 seconds, and the women's course record was set in 2009 by England's Chrissie Wellington with a time of 8 hours, 54 minutes, and 2 seconds.
What type of energy would the leg muscles of athletes that enter this race use during the final 26.2-mile foot race?

A) stored ATP and PCr
B) aerobic respiration
C) stored ATP and PCr plus lactic acid fermentation
D) lactic acid fermentation

Question 67

After reading the paragraph below, answer the questions that follow.
When sarcomeres contract, they generate force (tension). However, the amount of force generated depends on the sarcomere length and the amount of thick and thin filament overlap. Below is a figure that details the force-generating properties of a single sarcomere. This figure was modified from a scientific paper by Al Gordon and colleagues from 1966 and is a classic illustration of the relationship between sarcomere length and force.
Mammalian muscles can shorten approximately 35% of their resting length when all sarcomeres contract. If a sarcomere passes through maximal tension generation during this 35% contraction, what is the likely starting point for contraction of a sarcomere?

A) point A
B) point B
C) point D
D) point E

Question 68

After reading the paragraph below, answer the questions that follow.
The "Ironman" is a version of the triathlon, a race that includes three events: swimming, bicycling, and running. In an Ironman, an athlete must swim 2.4 miles, bike 112 miles, and run 26.2 miles, in that order, without a break. The annual Ironman World Championship is held in Hawaii every year. The men's course record was set in 2011 by Australia's Craig Alexander with a time of 8 hours, 18 minutes, and 37 seconds, and the women's course record was set in 2009 by England's Chrissie Wellington with a time of 8 hours, 54 minutes, and 2 seconds.
What type of muscle fibers would likely be found in the legs of athletes who attempt to complete this race?

A) fast, fatigue-resistant fibers
B) fast, fatigue-susceptible fibers
C) slow, fatigue-resistant fibers
D) slow, fatigue-susceptible fibers

Question 69

After reading the paragraph below, answer the questions that follow.
When sarcomeres contract, they generate force (tension). However, the amount of force generated depends on the sarcomere length and the amount of thick and thin filament overlap. Below is a figure that details the force-generating properties of a single sarcomere. This figure was modified from a scientific paper by Al Gordon and colleagues from 1966 and is a classic illustration of the relationship between sarcomere length and force.
At what point on the graph are thick and thin filaments most overlapped?

A) point A
B) point B
C) point D
D) point E

Question 70

In the year 2000, it was estimated that the number of new osteoporotic fractures in men and women ages 50 and older was 9.0 million: 1.6 million were at the hip, 1.7 million were at the forearm, and 1.4 million were from the spine and humerus. Consider the following data and answer the questions that follow.
Estimated Number of Fractures (in Thousands) Worldwide at the Sites Shown in Men and Women in the Year 2000
$\begin{array}{l}\quad\quad\quad\quad\quad\quad\quad\quad\text { Percentage of }\\\begin{array} { l l l l l } \text { Site of Fracture } & \text { Fractures } & \text { Men } & \text { Women } & \text { Total } \\\text { Hip } & 18.2 & 490 & 1,137 & 1,627 \\\text { Forearm } & 18.5 & 332 & 1,328 & 1,660 \\\text { Spine } & 15.8 & 554 & 862 & 1,416 \\\text { Humerus } & 7.9 & 178 & 528 & 706 \\\text { Other sites } & 39.6 & 1,909 & 1,641 & 3,550 \\\text { Total } & 100 & 3,463 & 5,496 & 8,959\end{array}\end{array}$ Source: Adapted from Johnell, O., & Kanis, J.A. (2006). Osteoporosis International, 17(12): 1726. doi:10.1007/s00198-006-0172-4.

-Combined fractures in the hip, forearm, spine, and humerus were

A) greater in women than men.
B) greater in men than women.
C) equal in men and women.

Question 71

After reading the paragraph below, answer the questions that follow.
When sarcomeres contract, they generate force (tension). However, the amount of force generated depends on the sarcomere length and the amount of thick and thin filament overlap. Below is a figure that details the force-generating properties of a single sarcomere. This figure was modified from a scientific paper by Al Gordon and colleagues from 1966 and is a classic illustration of the relationship between sarcomere length and force.
At what point on the graph is the sarcomere the most extended?

A) point A
B) point B
C) point C
D) point E

Question 72

In rickets, lack of calcium decreases the strength of the mineral matrix of compact bone so that it is unable to

A) resist compression.
B) complete extension.
C) complement muscle contraction.
D) bend at the joints.