题目内容：

语法填空

阅读下面的短文，在空白处填入一个适当的词，或填入括号中所给单词的正确形式。

Do you chew gum after a meal? _1.__( chew ) gum helps you clean your mouth. But some people spit（吐）chewing gum on the street instead of putting it in the garbage bin. It’s bad _2.___ the gum is sticky（黏的. It’s hard to get it off things.

__3._ ( recent ), a team of British scientists said they had solved the problem. They invented non-stick chewing gum.

In Britain, ￡150 million is _4._ ( spend ) to clean gum from the country’s streets each year. It’s the same in China. On Beijing’s Tian’anmen Square, after the National Day Holiday, __5.__ ( hundred ) of thousands of chewing gum pieces __6.__ ( be ) left on the ground. It usually takes weeks to clean them up.

But the non-stick is ___7._ ( easy ) to clean. It is washed away by the rain and it’s no problem for street cleaners. Even if you get the non-stick gum in your hair, you can wash it out __8.__ shampoo ( 洗发水 ).

“The gum is coated with a thin film of water,” said Professor Cosgrove, the 9.__ ( lead ) of the study. “That’s _10.__ it is not sticky at all.”