Mr. Smith his pupils how to prepare for the test since 8 am but no one listens to him.A.

问题补充：

Mr. Smith his pupils how to prepare for the test since 8 am, but no one listens to him.

A. has told

B. is telling

C. has been telling

D. will have told

答案：

A. has told

B. is telling

(答案→)C. has been telling

D. will have told

解析：句意：Mr.Smith从早上8点开始就一直在不停地告诉学生们如何准备考试，但没有一个学生听他讲。空处的动作从过去某一时间开始一直延续到现在，可能还要继续下去，因此应用现在完成进行时。故答案选C。