The Most Energy- Efficient Form of Transportation in the Animal

The most energy- efficient form of transportation in the animal kingdom is a human on a bicycle. A basic physics principle that helps explain the bicycle's high efficiency [relative to other technologies for human transportation] is

A) the second law of thermodynamics.
B) the work- energy principle.
C) the law of gravity.
D) the electromagnetic force law.
E) the law of conservation of energy.