We have made ______ clear that we are strongly against smoking in the office.

—Has_______of you learned the songYesterday Once More?—No，sir.Lewis is a new comer.

The chairman thought ___ necessary to invite Professor Smith to speak at the meeting . 

Our city has changed a lot; who can tell what it will be like in ___ ten years?

Those who brig sunshine into the lives of others cannot keep     from themselves.