Because the financial review covered only the fiscal years of July 1992 through June 1994, so the investigators were unable to determine the extent of possibly earlier overpayments.
Test points: scentence structure
(A) 1994, so the investigators were unable to determine the extent of possibly (
“becasue the financial...” is a subordinate clause, which is not a complete scentence, it has to modify the main clause. "So the inverstigators...“ constitute another subordinate clause, so there is no main clause in A)
(B) 1994, and the investigators were unable to determine the extent of possibly (
"and" is used to connect two independent clauses. Also, the meaning of this sentence does not make sense)
(C) 1994, the investigators were unable to determine the extent of possible
(D) 1994, therefore the investigators were unable to determine the extent of possibly (
same reason as A. Moreover, "therefore" makes the scentence redundant)
(E) 1994; therefore, the investigators were unable to determine the extent of possible (
same reason as A. Moreover, "therefore" makes the scentence redundant)