In the past twelve months the research members the effectiveness of many materials in a h

问题补充：

In the past twelve months the research members the effectiveness of many materials in a home building.

A. had studied

B. would study

C. studied

D. have studied

答案：

A. had studied

B. would study

C. studied

(答案→)D. have studied

解析：考查时态。根据时间状语in the past twelve months在过去的12个月，用现在完成时，故选D。