1. all of the following are physical responses to relaxation except
a. your blood pressure and heart rate decrease. b. your digestive system returns to normal functioning. c. you breathe more deeply, exhaling carbon dioxide that can make you feel anxious. d. your muscles remain ready for fight or flight.

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