The government is trying to ______ pollution to an even lower level so that we can have a better environment.
—Which of the two computer games did you prefer?—Actually I didn’t like .
—I’m going to Thailand this summer holiday.—
She always come to our help when we get into trouble ____ she is very busy.
He has three brothers, ________is a doctor.
As teenagers of the 21st century, we should be ready to _____ the challenge of society.