You can’t get good grades______ you study hard.

Microblog（微博） with so many people is sure to influence our society..

Why would some workers in Foxcon die __________ continue working in the factory —Psychologists say they are under too much pressure.

__________ does he improve his reading speed— He improves it ________ practicing more.

To make our city more beautiful ,rubbish ______ into the river.