Use reasoning to answer the following question.
Mammals generate heat mainly by what?\nOptions:\n- (A) hugging mammals\n- (B) calorie counting\n- (C) with their fur\n- (D) energy of moving objects\n- (E) burning calories\n- (F) sweating\n- (G) selling fur coats\n- (H) flow of electrons

(E)
Mammals generate heat mainly by keeping their metabolic rate high.

And resting metabolic rate is a big contributor to calories burning.

Mammals generate heat mainly by burning calories.

.

So, the answer is (E)