The manager __________the workers how to improve the program since 9 a.m.

2023-05-26

A.has told
B.is telling
C.has been telling
D.will have told

参考答案:C

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,应用完成进行时,故答案为C。