句子改错：GWD-3-Q30

Today’s technology allows manufacturers to make small cars more fuel-efficient now than at any time in their production history.

A. small cars more fuel-efficient now than at any time in their

B. small cars that are more fuel-efficient than they were at any time in their

C. small cars that are more fuel-efficient than those at any other time in

D. more fuel-efficient small cars than those at any other time in their

E.more fuel-efficient small cars now than at any time in

why not D? The correct answer is C. But according with OG, is D better?