Potential subjects should be informed of the research and _______ an opportunity to decide

Potential subjects should be informed of the research and _______ an opportunity to decide if they want to participate。

A.gave

B.giving

C.give

D.be given

答 案：D
考查动词的语态。后半句的主语是代词they，谓语动词是give，根据句意应是“他们被提供机会决定是否要参与研究”，故用被动语态。