— Where is John? — He in the library.A. should be B. must beC. can be D. must have been

问题补充：

— Where is John? — He in the library.

A. should be

B. must be

C. can be

D. must have been

答案：

A. should be

(答案→)B. must be

C. can be

D. must have been

解析： must do表示对现在的事实进行推测。