The chairman thought necessary to invite Dr. Smith to speak at the meeting.A. thatB. itC.

问题补充：

The chairman thought necessary to invite Dr. Smith to speak at the meeting.

A. that

B. it

C. this

D. him

答案：

A. that

(答案→)B. it

C. this

D. him

解析：考查固定句型：think it+adj +to do，it是形式主语，不定式是真正的主语，句意：主席认为有必要邀请斯密斯博士来到会议上演讲。选B。