18. using carbo-loading to increase the store of glycogen seems to benefit only those athletes who engage in aerobic activities that are
a. more than 90 minutes.
b. between 50 and 80 minutes.
c. between 30 and 60 minutes.
d. less than 20 minutes.

I believe the answer is: A. more than 90 minutes

This happen because muscles would typically depleted of oxygen after 90 minutes of continuous exercise. Because of this, carbo loading for less than 90 minutes exercise would only add unnecessary calories that might prevent you from reaching your goal.

addictive games maybe