Micro-letters (Weixin) will be charged has not been decided yet.

It isn't decided yet _______ we will attend the meeting.

—Mary looks down today. What is up?
—Well，________happened between Mary and me is none of your business.

thecity’spublicschoolsystemshouldbeopentothechildrenofmigrantworkershas become the focus of discussion.

__________knowledge comes from practice is known to all.

_______ parents say and do usually has a life-long effect on their children.  

______ leaves the room last ought to make sure that the windows are closed and the door locked.

______ is a fact that English is being accepted as an international language.

        some people regard as a drawback is seen as a plus by many others.

___________ David showed the report to the public surprised me.
A What   B. That   C. Which   D. Who