What do you mean by saying there are only ten tickets?There be twelve.
Some people fear that ________ air pollution may bring about changes in _______ weather around the world.
The doctor must be _______ 24 hours a day, 7 days a week in the boarding school.
What was considered impolite years ago has become ________now.
Which way do you enjoy _______ the coming winter holiday, staying home or going on a trip to Europe?
_______ worries the public a lot the way the students are getting more and more stressed out.