参考范文：

　　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