He is one of the students who I am sure always do best.A. theirB. one’sC. myD. his

问题补充：

He is one of the students who, I am sure, always do best.

A. their

B. one’s

C. my

D. his

答案：

(答案→)A. their

B. one’s

C. my

D. his

解析：句意：他是做，我确定，总是竭尽全力的学生之一。try ones best

“尽某人最大的努力。这是一个定语从句，从句的主语是students，因此要用their，故选A。