5.A good teacher is ________who is always doing things for the good of the students.
The scientist decided to devote his life to ____ pollution from ____ again.
Tom kept silent about the accident _________ lose his job.
Iraq has ______ too many wars since 1990, making his people _______ a lot.
As is known to all, China _______the group of developing countries.
We find _______ difficult to talk to him about anything serious.