-- Who do you think the book here?
--- It may be John. He was sitting here all the morning.
A. has left
B. leaves
C. had left
D. was leaving
网友回答
(答案→)A. has left
B. leaves
C. had left
D. was leaving
解析：考查时态。句意：你认为是谁把书留在这儿了？——可能是约翰。整个上午他都坐在这儿。结合语境可知上文从句描述的是现在已经完成的动作，故用现在完成时态，选A。