【题目】Various efforts ________ in the past decades to protect the environment.
A. had made B. have made
C. were made D. have been made
在线课程【答案】D
【解析】考查时态和语态。句意：在过去的几十年里，为保护环境做出了各种努力。根据in the past decades可知句子用现在完成时态，efforts是句子主语，复数形式，和谓语动词make之间是被动关系，所以此处用现在完成时态的被动语态，故答案为D。