The chances that a sibling of a schizophrenic individual will also be schizophrenic are fairly high, about 8 in 100. This does not show that schizophrenia is inherited because __________.

A) if it were, the risk would be much closer to 100%
B) the level of risk is about the same in the general population
C) siblings usually grow up in the same environments
D) all of the above