请教关于比较时助动词补出的问题！

53.  (27280-!-item-!-188;#058&003467)

Britain's economic growth was slower in the mid-1970's and its decline much more rapid in the subsequent recession than the United States.

(A) Britain's economic growth was slower in the mid-1970's and its decline much more rapid in the subsequent recession than the United States.

(B) The economic growth of Britain was slower in the mid-1970's and it declined much more rapidly in the subsequent recession than the United States did.

(C) Britain's economy, which grew more slowly in the mid-1970's, also had declined much more rapidly in the subsequent recession than the United States did.

(D) The economy of Britain grew more slowly in the mid-1970's and declined much more rapidly in the subsequent recession than did the economy of the United States.

(E) Britain's economy grew more slowly in the mid-1970's and its decline was much more rapid during the subsequent recession than the economy of the United States.

这道题答案是D 我也看着D挺顺眼的 但是than之前出现了两个动词 会不会导致than之后的did补出出现歧义？不知道是补的哪个动词？望NN指点

did代表2个动词