She is my best teacher ______ help I have made great progress.
The atmosphere of the earth ______ us from the strong sun light.
---How well did John do in the match? --Wonderful. I think we can’t have a ______ player in our football team.
Many countries are increasing their use of natural gas , wind and other forms of ______.
The fact that many college graduates get lower pay than some workers has ______ a heated discussion.
I have no idea ______ it is that makes him puzzled.