Why Is the Body Temperature Maintained at About 37°C

Why is the body temperature maintained at about 37°C?

A) That's the easiest to maintain given the average temperatures in our habitat.
B) That's how much heat our metabolic processes can produce.
C) That's the temperature at which our metabolic processes are most efficient.
D) That's the average body temperature of all animals.
E) That's the temperature that kills most pathogens.