Explain why exercise programs must increase in difficulty and duration over time to remain effective

Your body becomes used to the intensity and will therefore render the program useless.

Bisexual is when you like boys and girls.i hope that

(a) is not correct because one does not get increased cholesterol  from lifting weights.(b) is not correct because lifting weights cannot reduce the risk of a hereditary disease.(c) is not correct because back pain isn't a benefit! and plus, if he lifts weights properly, he should not have back pain.(d) is the correct answer because his ligaments will gain mass, making it easier for him to carry heavier weights and he will also be stronger!