请教that在此句中修饰哪一个名词？

asd135710

A 1972 agreement between Canada and the United States reduced the amount of phosphates that municipalities are allowed to dump into the Great Lakes.请问that修饰的是amount 还是 phosphates？ 如果是amount，那么that 后面的从句还原之后会是什么样子？ Municipalities are allowed to dump the amount of phosphates into the Great Lakes?  dump 能跟 amount？ 还是我理解错了呢？ 谢谢！

asd135710

源于一个OG争议老题，解释各种各样。
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


有人说不选A是因为不能reduce在reduce这个动作发生的那个时间点的过去已经倒掉的amount。
我想知道that真的修饰amount吗？

kiwifoodtown

OG 解释的很清楚，修饰phosphates。