Read the following sentence and choose the best alternative which should replace the italicized part of the sentence.
Economic theory fails 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