Who do you think the book here?It may be John. He was sitting here all the mornin

问题补充：

--- Who do you think the book here?

--- It may be John. He was sitting here all the morning.

A. was leaving

B. leaves

C. had left

D. has left

答案：

A. was leaving

B. leaves

C. had left

(答案→)D. has left

解析：强调过去发生的动作对现在造成了影响—书留在了这里，应该用现在完成时。