PT 62 S2 Q9

A retrospective study is a scientific study that tries todetermine the ... ...

Which one of the following, if assumed, enables the argument's conclusion to be properly drawn?
(A) Whether or not a study of human subjects can reliably determine the causes of those subjects' present characteristics may depend at least in part on the extent to which that study uses inaccurate reports about the subjects' pasts.
(B) ...
(C) ...
(D) ...
(E) ...

*This question is included in Complete Section: LR-A, Dec. '10 LSAT (PT 62 Sec. 2)