He would have been a doctor 20 years ago but he to be a teacher.A. choosesB. choseC. had

问题补充：

He would have been a doctor 20 years ago, but he to be a teacher.

A. chooses

B. chose

C. had chosen

D. has chosen

答案：

A. chooses

(答案→)B. chose

C. had chosen

D. has chosen

解析：考查虚拟语气和时态。But后面的句子要使用陈述语气，共计前半句的would have been说明本题是与过去相反的虚拟语气，故But后面要使用过去时。故B正确。