求解OG12 第74，不理解，求帮助

tczhanghuan

74. 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
选D

1法律之类的不一般都用现在时吗？ 这里咋用过去式？
2D里面的recuded是过去式， that从句中用are allowed的现在时正确吗？

sisichen666

1.描述法律的具体内容的时候law+doing（作为修饰语出现），这道题直接reduced作为谓语动词没有问题，因为出现in 1972的修饰——决定一般过去时，根据逻辑含义也不难判断，是1972年的agreement减少了合法的P的排除量
2.这就要根据句意来理解了，既定法规约束的是未来的行为，而不是过去的行为，所以The allowed amount of P一直延续到现在还是在使用的，因此用are

joyzhang1990

An agreement that occurred in 1972 is correctly described with the past tense verb reduced.Since the dumping continued after the date of the agreement，the past perfect verb had been allowed should instead be the present are allowed（if the agreement remained in effect when the sentence was written）or the past were allowed （if the agreement was no longer in effect when the sentence was written）
A mission-critical modifier
that修饰 the amount of phoshphates 这整个名词组

tczhanghuan

豁然开朗，太感谢啦