题目内容：

适当形式填空(短文适当形式)

The smell of gas on the street may make us hold our breath. However, when it comes to 1. (pollute), your own home may be just bad.

"People spend most of their time indoors, and 2.(they) homes can be two to five times as polluted as the air outside," says the US Environmental Protection Agency.

Poor indoor air quality can cause health problems. And a lot of these problems 3.(cause) by something in your house. 4.(make) your home healthy, here are some useful tips:

Is the fan in your bathroom 5.(work) well? Turn it on. Put a sheet of paper against it. If the paper sticks, the fan is strong enough. If not, it needs to be repaired. A good fan 6.(make) sure the air in the bathroom is fresh.

Keep your gutters(水槽) clean and clear so that dirty water doesn't make your kitchen or bathroom 7.(smell) bad.

And 8.(not leave) the litter in bags or bins in your home. The place for it is outside, waiting for collection.

When you are at home, open the windows 9.(let) fresh air in.

Follow these simple steps, and you're sure to live in a 10.(health) environment.