The chairman thought necessary to invite Professor Smith to speak at the meeting.
A. that
B. this
C. it
D. which
网友回答
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。