问题
选择题
-- 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
答案
答案：A
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。