A key finding of research on aggression is that it is

A key finding of research on aggression is that it is
 
  a. controlled by the amount of testosterone a person has, which is why men are more aggressive than women.
  b. controlled by the posterior hypothalamus, and if someone has a problem with excessive aggression, they probably have a malfunction there.
  c. the result of a combination of biological, psychological, and social factors with different factors being most important under various circumstances.
  d. a result of environment, and that children who are not exposed to violence will not be violent.