If Tom's 1RM on Bench Press is 200 pounds and he is completing a workout listed as: Bench Press 50% 4 x 10

What is the Intensity for this exercise in pounds?

100lbs because if his max is 200 and he is doing 50% of his max that equals 100

Ibelieve it's choice d.

Because without physical activity, the body has extra "energy" if you will, and so when it is time for bed you are not tired, so you end up staying up all night. also there is probably an effect on your internal clock, which messes with your melatonin production which goes hand in hand with your sleep cycle