It is ___ the customers’ needs that has made chain stores so popular in big cities in China.
To those scientists, it still remains to be a question ______ man can go back to the old days with time machine.
There is a common belief among them _______ rubbish can and should be put into good use.
We never doubt ______ our school team will win the match against No. 3 Middle School.
The teacher usually grades the students on _______ they have behaved.
Once _____, it won’t be easily forgotten.