The following questions present a sentence

问题：

The following questions present a sentence, part of which or all of which is underlined. Beneath the sentence, you will find five ways of phrasing the underlined part. The first of these repeats the original; the other four are different. If you think the original is best, choose the first answer; otherwise choose one of the others.

These questions test correctness and effectiveness of expression. In choosing your answer, follow the requirements of standard written English; that is, pay attention to grammar, choice of words, and sentence construction. Choose the answer that produces the most effective sentence; this answer should be clear and exact, without awkwardness, ambiguity, redundancy, or grammatical error.

Professor Markham’s theory falls to explain the extent to which savings from personal income has shifted to short-term bonds, money-market funds, and other near-term investments by the instability in the futures market.（）

A. to which savings from personal income has shifted

B. of savings from personal income that has been shifted

C. of savings from personal income shifting

D. to which savings from personal income have shifted

E. to which savings from personal income have been shifted