(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

该题的答案,ETS认为答案不是A,而是D.

ETS是这么解释的(下面原文照抄):

Verb form + Idiom

An agreement that occurred in 1972 is correctly described with the past tens verb reduced.Since the dumping continues into the present, the past perfect verb had been allowed should instead be the present are allowed.

A Had been allowed should be are allowed.

B The phosphbates amount should be the amount of phosphates;the meaning of the sentence is changed by the omission of any form of allow.

C The present tense reduces should be the past tense reduced;the phosphate amount should be the amount of phosphates;have been allowed should be are allowed

D Correct.The past tense reduced is correctly used in this sentence to describe a past action,and the present tense are allowed is used to describle the present situation.

E The present tense reduces should be the past tense redueced;allowed for dumping is an incorrect idiom;allowed for dumping by municipalities is awkward

The correct answer is D.

我这样理解A答案：1972年之前，允许了一个倾倒量，在1972年协议达成之后，减少了这个允许的倾倒量，“减少”发生在过去（1972），则用reduced，那么allow用过去完成事态表示允许（allow）这个动作发生在1972年之前。

我哪里理解错了？请nn们指教！

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.

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

浅见： 表面上看，应该用过去完成时而选择A。但是想想过去允许的倾倒量怎么可以在之后的时间，也就是1972年，通过协议的方式减少呢？

题目的希望表达意思是：美加之间通过一个协议，协议做什么的呢？---- 减少phosphates的量。这是什么样的量？周边城市被允许向大湖中倾倒phosphates的量。这个条款在协议发布后一直生效，所以用一般现在时。