Which energy transformations best illustrates why people can walk? a) chemical energy is being converted into light energy. b) chemical energy is being converted into thermal energy. c) chemical energy is being converted into mechanical energy. d) chemical energy is being converted into more chemical energy.

The answer is letter c.

The explanation behind this is when human consumes a plant or when a human being eats an animal that ate a plant. The chemical energy kept in the plant (or animal) cells is progressed into the cells of the human's body. All of the body progressions, like ingestion, breathing, pumping blood, are driven by cells changing the kept chemical energy into heat and work, in a procedure called respiration. In the muscle cells of the human (or any animal), the chemical energy is converted into mechanical work and heat. The muscle pacts, the legs thrust, and the body jumps into the air. 

No because a circle or pie graph usually shows percentages you'd need a line graph

W= fd
where f is an applied force and d is the distance over which it is applied. when a parachuting skydiver is at constant velocity, he is experiencing "terminal velocity", the point at which his acceleration down is canceled out by air resistance. that means that the resisting force of the air is equal to his weight, but in the opposite direction. with this, we can solve for the work done by the force.
w = fd
w = (92.0)(9.81 m/s^2) (325)
w= 2.93 x 10^5 j
the value for work in this case is positive because it is pushing up on the skydiver, who has a downward force of gravity.
therefore the answer is 2.93 x 10^5 j