As civilization __________,more and more people have realized the importance of preserving rare animals from dying out.
The murder was brought in, with his hands ___ behind his back。
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.