OG11和大全答案矛盾的一道题

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

这道题大全的答案是(A), OG 的答案是(D), 我觉得应该是(D), 因为颁布的法案用现在时态,只能表示对现在和将来的影响, 可如果用" had been allowed to dump"那么就成限制以前的动作了,对以前的动作的影响, 逻辑是讲不通哦~~~

请教大家的看法, 我哪想错了呢?