Which of the following is true about protein and supplements in diets?
a. everyone needs additional protein in their diet.
b. weight lifters need to include supplements in their diets.
c. it is uncertain whether many dietary supplements are effective.
d. most supplements are known to enhance the benefits of weight training.

The answer is C. It is Uncertain whether many dietary supplements are Effective

Losing weight is no Rocket Science. Your body have to burn more than what it get. So we have to lower our calories intake and let the body burn our fat as a source of energy. If there are any Pills that tell you that you could lose weight without watching your calorie intake, it's a scam

Ican only answer your first question, a machine is like a human body because it's a little similar. they both almost work like the same.