本贴相关题目 OG-2015-SC-77OG-2015-SC-77
OG-13-SC-77
OG-12-SC-74
... (DFTP)

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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.

Areduced the amount of phosphates that municipalities had been allowed to dump
Breduced the phosphate amount that municipalities had been dumping
Creduces the phosphate amount municipalities have been allowed to dump
Dreduced the amount of phosphates that municipalities are allowed to dump
Ereduces the amount of phosphates allowed for dumping by municipalities

正确答案: D

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crystal509

电梯直达

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发表于 2011-10-27 14:32:41 | 显示全部楼层回帖奖励

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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
答案为D
我想问为什么这里不能用现在完成时呢？