He is the only one of those clerks to the important conference. A. who was invitingB. who

问题补充：

He is the only one of those clerks to the important conference.

A. who was inviting

B. who were invited

C. who has been invited

D. who have been invited.

答案：

A. who was inviting

B. who were invited

(答案→)C. who has been invited

D. who have been invited.

解析：句意：他是唯一的一个被邀请参加重要会议的办事员。这里是定语从句，先行词是the only one，因为主句用的是is，invite与主语之间是被动关系，故排除A，who在从句中作主语，谓语动词的单复数应与先行词一致，所以应该用单数，故排除BD，故选C。