The manager the workers how to improve the program since 9 am.
A. has told
B. is telling
C. has been telling
D. will have told
网友回答
A. has told
B. is telling
(答案→)C. has been telling
D. will have told
解析：现在完成进行时表示：过去某一动作从过去开始一直延续到现在，现在刚刚结束或还在进行。句意：经理从早上9点开始就一直在不停的告诉工人们如何改进这个项目。根据句意选C。
【考点定位】考查动词时态。