When it______air pollution, Beijing faces the three “C” s-----cars,coal and construction,which lead to Beijing's thick air pollution.
Is it easier to make plans _____ trips now?
The question is not easy _____.
The classroom ______ 30 feet long.
As middle school students, we _____ the police to keep order.
The teacher said he needed _____ boys besides his students _____ the classroom.