When your body burns calories more efficiently, you
a. decrease the amount of muscle mass and increase the amount of body fat.
b. increase the amount of muscle mass and decrease the amount of body fat.
c. lose all your body fat.
d. exercise without fatigue.?

B or C

Explanation:

Fat is an energy storing nutrient so you would burn out all the kilocalories of Fat before burning out anything else. It depends on what exercise youre doing and just burning calories doesnt mean youre also building and working out your muscles. You need to put your muscles under pressure for the mass to increase. In my opinion since no exercise is said in the question you would only lose your body fat as it didnt specifically mention exercise