Exhaustion of energy reserves or decline in pH due to production and dissociation of lactic acid causes muscle contraction. the conduction of neural information to the A. muscle fiber.
B. muscle fatigue.
C. muscle relaxation.
D. the striated appearance of skeletal muscle.

Depression would be the correct answer

(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!

Well i guess u know a lot of that, huh? that's nasty of me, isn't it? lol