假设你是李华，David是你的美国网友。他对目前中国出现的雾霆天气很关注，来信向你询问此事。请你给他写封回信。主要内容如下：1.感谢他的关注。2.简介雾霾 (smog) 天气给人们的身体、生活带来的危害。3.谈谈你的感想。注意：可适当增加细节，以使行文连贯流畅;开头与结尾已写好，不计人总词数; 词数：120左右。
​Dear David，

I'm glad to receive your letter. _______________________________________

Yours，

Li Hua

参考范文：

Dear David,

I'm glad to receive your letter. I have learned from your letter that you are concerned about the smog which frequently appears in some areas of China. Thank you for your concern. I'm also very worried about such terrible weather because it has brought much inconvenience or rather harm to people's health such as traffic jam, road accidents, bad coughs, throat hurts and ever lung cancers and so on.

As everybody knows, a good environment comes from good protection. So we should do what we can to make a difference. Try to drive less and choose air-friendly products. Only when everyone has the environmental awareness can we have cleaner air.

Hoping to hear from you soon and share your good ideas.