2. 垃圾须分四类(干、湿、可循环、有害) ；
参考词汇：垃圾分类 trash sorting
Having learned that you are interested in the trash-sorting program promoted recently in China, I am here writing to give you a brief introduction.
As far as I know, Shanghai has become the pioneer of our country's waste sorting policy. As of July 1st this year, the residents in Shanghai have not been able to dump their waste bags in whichever bin was closest. On the contrary, domestic waste is required to be classified into four categories: dry refuse, wet trash, recyclable waste and hazardous(dangerous) waste.
Faced with the new rule, many citizens in Shanghai are finding it a little too complicated, with every item of waste now under careful scrutiny(examination) and classification. Still, there are more people who warmly support the policy because it helps people to cultivate greener lifestyle habits and helps China to become a more beautiful country.