When Someone Says That There Is a Gene for a Behavior

When someone says that there is a gene for a behavior, they most likely mean that

A) the gene is solely responsible for the development of that behavior.
B) individuals with different forms of that gene exhibit different behaviors.
C) the role of the environment in affecting the development of the behavior is relatively small.
D) the behavior is unlikely to respond to selection, since there is no variation in the species.