请教大侠们一道《OG12版》与《白勇语法全解》有分歧的题！！

michaels7

最近准备语法时做到一题很困或：
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

OG12版的P671, 74题的答案解释为D, 但是白用语法全解的第四章 动词形式 的第三道习题，解释为A
我觉得A更为正确啊～～～麻烦大侠帮忙～～～～～

michaels7

呵呵～～自顶一个～觉得三楼的解释有点道理～～～～～～仍期待权威来个了断呀～～吼～