询问一题

1.        A 1972 agreement between Canada and the United States
                    reduced the amount of phosphates that municipalities had been allowed to dump into the Great Lakes.

(A) reduced the amount of phosphates that municipalities had been allowed to dump

(B) reduced the phosphate amount that municipalities had been dumping

(C) reduces the phosphate amount municipalities have been allowed to dump

(D) reduced the amount of phosphates that municipalities are allowed to dump

(E) reduces the amount of phosphates allowed for dumping by municipalities

大全中的答案是A， 但OG中的答案是D，到底是哪个答案！

大全的解释在OG选D的情况下还选A？？