Based on Research That Has Been Conducted So Far, What

Based on research that has been conducted so far, what can be concluded about the causes of sexual orientation?

A) Researchers cannot say with certainty why people become homosexual, bisexual, or heterosexual.
B) Most researchers are now convinced that sexual orientation is primarily the result of environmental influences.
C) Researchers are sure that homosexuality is caused by unpleasant early heterosexual experiences.
D) Most researchers are now convinced that sexual orientation is almost certainly caused by genetic factors and that other factors have little or no influence.