假设你是李华，David是你的美国朋友．．他对目前中国出现的雾霾天气很关注，来信向你询问此事，请你给他写封回信．回信从雾霾的成因，雾霾的危害以及如何做好自我保护三方面进行阐

Question

假设你是李华，David是你的美国朋友．．他对目前中国出现的雾霾天气很关注，来信向你询问此事，请你给他写封回信．回信从雾霾的成因，雾霾的危害以及如何做好自我保护三方面进行阐述．
写作要求：1.80词左右，开头已给出，不计入总词数；
2．不能出现真实的校名和人名，否则不得分；
3．写作要点都必须用上，紧扣主题，适当发挥．
参考词汇：smog（雾霾），reasons，disease，cancer（癌症），mask（口罩），environment
Dear David，
I'm glad to receive your letter．___
Yours，
Li Hua．

Answer 1

Dear David，
I'm glad to receive your letter．I'll tell you something about the smog．There are many reasons which caused smog．First，the smog has been caused by many factories．Second，the increase of cars in the city area plays an important role．The cars send off a lot of gases，and it adds to the already serious air pollution．（成因）The smog has done much harm to people's health．It can cause cancer．（危害）In my opinion，first，we can wear masks when we go out．【高分句型一】Then，we should use more public transport．Only in this way  can we  expect to have more sunny days．【高分句型二】（自我保护）
Yours
Li Hua