While Running a Marathon,Alain Stumbled and Fell

Multiple Choice

While running a marathon,Alain stumbled and fell.Despite feeling a sharp pain initially,he got up and continued to run until he completed the race.Upon crossing the finish line he fell down writhing in pain.When examined,it was discovered that Alain had broken his leg.He was able to run the remainder of the marathon relatively pain-free due to the release of

A) serotonin.
B) cortisol.
C) testosterone.
D) endorphins.