The Pilomotor Reflex Have You Ever Experienced the Pilomotor Reflex? Chances Are That

The Pilomotor Reflex
Have you ever experienced the pilomotor reflex? Chances are that you have. The pilomotor reflex is actually something most people experience every day: goose bumps.
Goosebumps (also called goose flesh and goose pimples) are small bumps on the skin. They are created when tiny muscles beneath the hairs on your skin contract, pulling the hair into an upright position. They can occur anywhere that you have hair on your body, but they are most common on your arms and legs. Goosebumps are an involuntary reaction to many different sensations, such as cold, fear, or even happiness.
Humans are not the only animals that get goosebumps. When cats or dogs are threatened by an enemy, the pilomotor reflex will cause their fur to stand on end. This makes the animal look larger, which might scare away the enemy. Porcupines also experience the pilomotor reflex; a frightened porcupine will raise its quills when it is in danger. This not only makes the porcupine look bigger, it frightens enemies away by drawing attention to the sharp quills. The pilomotor reflex can also help animals stay warm by trapping body heat closer to their skin.
Because human beings have much less body hair than most other animals, goosebumps do not make us seem larger or more intimidating. They also do not help to keep us very warm, although they do help to prevent some heat from leaving the body. For the most part, the pilomotor reflex is much more important for animals than it is for people. In fact, many scientists think that the pilomotor reflex is actually completely useless for humans.
Question: What is the author's purpose in writing this passage?

A) To encourage the reader to learn more about the pilomotor reflex.
B) To entertain the reader with a personal story about goosebumps.
C) To persuade the reader that the pilomotor reflex is not important for humans.
D) To describe the cause and varied effects of the pilomotor reflex.