Before using the lawn mower or other power equipment:

place your hands or feet near the rotating blades
clear the yard of people and pets
take off your shoes
put on a pair of shorts

Plasma with a clotting factor removed.

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

Ithink the answer is c.  hope this is right and