170。 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
(B) so therefore the investigators were not capable of determining the possible extent of
(C) therefore the investigators were unable to determine the possible extent of
(D) the investigators were not capable of determining the possible extent of（E）
(E) the investigators were unable to determine the extent of possible
如果把C 中的possible 的位置换为 to determine the extent of possible，那这个答案对吗？也就是说because 能和therefore连用吗？ | 
