假定你是李华，David 是你的美国笔友。他对中国鼓励使用环保购物袋很感兴趣，来信向你询问此事。请你给他写封回信。主要内容如下：
◇ 感谢他的关注。
◇ 简要介绍相关情况。
◇ 谈谈你的感想。
注意：
1. 词数100左右，信的格式已为你写好。
2. 可根据内容要点适当增加细节，以使行文连贯。
3. 参考词汇：环保购物袋---environment-friendly shopping bag; 关注---concern.

[范文]
Dear David,
　　I’m glad that you’ve noticed our efforts directed towards environmental protection. Thank you for your concern.
　　As too much use of plastic bags has caused serious white pollution, our govenment encourages us to use environment-friendly shopping bags. These bags are made of a variety of material that can be easily treated when they become rubbish. Besides, they can be reused. More and more people in China have realized the advantages of such bags and started using them.
　　I believe that the wide use of these shopping bags can greatly improve our environment. This is one of the many steps we are to make our country an even cleaner place.
Yours,
Li Hua