With Regard to the Concept of a "Gay Gene," the Textbook

With regard to the concept of a "gay gene," the textbook concludes that

A) there is strong evidence that a gene or small set of genes is responsible for a large percentage of the variance in the cause of same-sex sexual preference.
B) there is weak to moderate evidence that a gene or small set of genes is responsible for a large percentage of the variance in the cause of same-sex sexual preference.
C) any gene that is associated with sexual orientation will only confer a predisposition rather than definitively cause same-sex orientation.
D) there is currently no evidence to support the concept of genetic component to the cause of same -sex orientation.