The manager the workers how to improve the program since 9 a.m.
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：本题考查时态。句意为：从上午九点开始，经理在一直不停地告诫工人如何去完善这个项目。由时间状语since 9 a.m.可以先排除B和D；根据句意，此处需要的是“一直不停地告诫”，强调持续性，故完成进行时更好，所以答案选C。