"conservation of energy" refers to the fact that

a. the entropy of the universe is always increasing
b. energy cannot be created or destroyed but can be converted from one form to another
c. no chemical reaction is 100 percent efficient
d. the net amount of disorder is always increasing
e. if you conserve energy you will not be as tired

Option (b) is the correct answer.

Explanation:

According to the law of conservation of energy, it is known that energy can neither be created nor it can be destroyed.

But energy can be changed from one form to another.

Whereas entropy is the degree of randomness present within the molecules of a substance or object.

For example, gas molecules are able to move rapidly so, they have more entropy as compared to solid and liquid substances.

According to second law of thermodynamics, entropy of the system is always increasing.

Thus, we can conclude that "Conservation of energy" refers to the fact that energy cannot be created or destroyed but can be converted from one form to another.