We can never expect________bluer sky unless we create___________less polluted world.
—Jane always tries to ____. —That’s true. She always compares herself with her friends and neighbours.
It is the test system, rather than the teachers,_______ is to blame for the students' heavy burden nowadays.
—_____ do you like the match? —More exciting than _____.
Betty’s parents are away for the week, so I think I’d go over to keep her _____.
True friendship is like sound health, _____ value is seldom known until it is lost.