For many years people electric cars. However making them has been more difficult than pr

问题补充：

For many years, people electric cars. However, making them has been more difficult than predicted.

A. dream of

B. had dreamed of

C. dreamed of

D. have dreamed of

答案：

A. dream of

B. had dreamed of

C. dreamed of

(答案→)D. have dreamed of

解析： 考查时态。根据时间状语For many years,可知应用现在完成时态。所以选D。