NN看看这个题！

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（A）

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

为什么选A，不选B呢？

not NN

If I am right, the answer should be D~

With a past form to indicate that the law was in the past

with present tense to show what is required by the law~~~