A\

B\reduced the phosphate amount that municipalities had been dunmping

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 ofr dumping by municipalities

答案是A

我没有别的问题，只是想问一下关于这句话的时态判断。我一眼看到agreement就觉得是属于合同协议的客观作用，所以选择了reduces。结果解释上却说时间标志1972决定了谓语为reduced。。这个我也觉得有道理。。我想问一下是不是以后说XX年的协定，条约之类的都应该用过去时。还是有例外？？

it's both correct either to use "reduces" or "reduced" as long as you keep the tense consistent through out the sentence. The trick of the question is the consistency and the use of "allow". B is wrong because it doesn't say "the amount of", likewise C is wrong. D is wrong because the tense is not consistent. E is awkard because it says "phosphates allowed for dumping"