1. Because the financial review covered only the last few fiscal years, and therefore the investigators were unable to determine the extent to possible earlier overpayments.
(A) and therefore the investigators were unable to determine the extent to possible
(E) the investigators were unable to determine the extent of poss
请问a和e的最主要的区别是什么?我以为extent to which是固定搭配采选a的,可什么原因a错了呢?