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。请你给他回信。

1. 感谢他的关注

2. 简要介绍相关情况

3. 谈谈你的想法

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 government encourages us to use environmental –friendly shopping bags. These bags are made of a variety of materials that can be easily treated when they become rubbish. Besides, they can be reused. More and more people 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.