Aperson whose body can no longer keep up with the demands of stress is in the

A person whose body can no longer keep up with the demands of stress is in the exhaustion stage. At this point, there is not much this person can do anymore, and has to go and have a rest, or else there may be serious repercussions when it comes to that person's health.  

C= syphilis would be the answer

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