【问题】一道高一选择题Mr.Smith_______inthes
Mr. Smh _______ in the school twenty years by July. A.has worked B.worked C.has been wording D.will have worked 请说明原因，谢谢~
选择D 因为是by July 就是说在七月份之前,很明显七月份还没到.而这句话的意思是史密斯先生到七月份就已经在学校教了20年了,所以应该用将来完成时.