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 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
LZ,这道题OG的英英解释的非常清楚了,可以在仔细的看一下OG啊。
语法角度说的话,be done是用动作发出者的也就是by...,这里是municipalities are allowed to dump by A 1972 agreement,说明dump这个动作是agreement出台后才有的,所以过去完成时不能用。