Sentence Correction

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

can anyone plz give me the right answer.

Thanks.

The answer is D

thanks. but can u explain why

Reva wrote:thanks. but can u explain why

(A) reduced the amount of phosphates that municipalities had been allowed to dump - The reduced amount stays good even in the present. This option seems to imply that the reduction in the amount of phospates was in the past and that the agreement doesnot hold good now.
(B) reduced the phosphate amount that municipalities had been dumping - 'phospate amount' is awkward
(C) reduces the phosphate amount municipalities have been allowed to dump - 'phospate amount' is awkward
(D) reduced the amount of phosphates that municipalities are allowed to dump - correct. specifies the meaning as intended by the author.
(E) reduces the amount of phosphates allowed for dumping by municipalities - wrong because allowed for dumping implies the wrong meaning. It kinda implies that phospate is a tool that is used for dumping something

Helps ?

thanks for the explanation