You must keep us of how things are going here.A. informingB. informedC. informD. to info

问题补充：

You must keep us of how things are going here.

A. informing

B. informed

C. inform

D. to inform

答案：

A. informing

(答案→)B. informed

C. inform

D. to inform

解析：考查固定搭配。inform sb of sth通知某人某事；inform sb to do sth/that通知某人做某事；keep sb informed of sth让某人知晓......。句意：你必须让我们知晓事情的发展状况。故选B。