题目如下：
62. 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
分析如下：
Verb form + Idiom
An agreement that occurred in 1972 is correctly described with the past tense 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 phosphate 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 describe the present situation.
E The present tense reduces should be the past tense reduced; allowed for dumping is an incorrect idiom; allowed for dumping by municipalities is awkward
我的问题是：为什么用reduced，而不用reduces？这种主句和从句时态不一致的情况感觉很微妙，不好把握。谢谢 | 
