It is by no means clear ________ the president can do something to end the strike.

Professor Li always allows his students to voice their opinions in class, ______ sometimes their opinions are not sound.

.It was the practice _____ he got abroad _____ made him a good English speaker.

They are putting too much carbon dioxide into the atmosphere, ______ prevents heat from escaping from the earth into space.              

I don’t know why you’re worried about it. ________, it’s none of your business.