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

问题补充：

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

A. that

B. this

C. it

D. which

答案：

A. that

B. this

(答案→)C. it

D. which

解析：句意：主席认为邀请斯密斯教授在会上发言是必要的。it是形式宾语，to invite Professor Smith to speak at the meeting才是真正的宾语。句型是：think It necessary to do sth“认为做…是必要的“，选C。