Question ID:PT20 S4 Q21 Passage:Wirth:  All efforts to identify a gene responsible for predisposing people to manic-depression have failed.  In fact, nearly all researchers now agree that there is no "manic-depression gene."  Therefore, if these researchers are right, any claim that some people are genetically predisposed to manic-depression is simply false.Chang:  I do not dispute your evidence, but I take issue with your conclusion.  Many of the researchers you refer to have found evidence that a set of several genes is involved and that complex interactions among these genes produce a predisposition to manic-depression. Stem:The point at issue between Wirth and Chang is whether Correct Answer Choice:DChoice A:efforts to identify a gene or set of several genes responsible for predisposing people to manic-depression have all failed Choice B:it is likely that researchers will ever be able to find a single gene that predisposes people to manic-depression Choice C:nearly all researchers now agree that there is no manic-depression gene Choice D:current research supports the claim that no one is genetically predisposed to manic-depression Choice E:the efforts made to find a gene that can produce a predisposition to manic-depression were thorough