He（ ）four lectures on modern philosophy, but he only gave two because of his illness.
A、
would give
B、
had given
C、
should have given
D、
must have given
【正确答案】：C
【题目解析】：
本题考查虚拟语气。
根据but后边的gave可知是对过去的虚拟。语境为”他本应该上四节课“。should+have done 表示对过去的虚拟，本应该...。故选C。
句意：他本应该讲四次现代哲学，但因为生病，他只讲了两次。
