The basal metabolic rate measures the rate at which a person's body burns food and nutrient __ A.
at rest
B.
under stress
C.
while exercising
D.
on average

A. at rest

Explanation:

The "Basal Metabolic Rate" (BMR) is an important indicator that will help you know how many calories you actually need to eat every day in order to lose, gain or maintain your weight. It tells you the rate at which your body is burning calories while it is resting. The energy is then used for basic human survival like breathing, pumping of the heart and so on. It increases with exercise, which means the more you exercise, the more likely your BMR will increase or the more likely you'll burn calories while at rest.