If there is pollution, the air in our city will be dirtier.

Not only can ______shut-eye leave us feeling tired and lazy but it can also be damaging our health and looks.

The iphone 4s, ________ by Apple, sells well across the world.

It’s a __________day today. Let’s go _________.——Great. Let’s go.

1—________ cold weather!—Yes, it is. You should wear warm clothes.