The driver has much experience of driving, and _____ he behaved very calmly in the dangerous situation.

Although modem organic food has become very popular, many people can' t figure out the difference between organic foods and ______ grown foods．

 He put on his tie, took one last look at the room and_____________  walked out of the door.

It is the prevention of disease______its successful treatment that has led to the rapid increase of the world’s population.

----What about going on a trip?----Sound a good idea. But I don't have time now and____it's too expensive.