Nowadays, email has become more and more popular. Most people prefer email to writing letters. Maybe it is because email has more advantages than writing letters. First of all, email is more convinient,accurate and fast. People can write letter to anyone in anywhere only if they can search the Internet. If the email adress is correct, the email can reach the destination in a few seconds without worrying lost on the way or arrive at after a long time. In addition, it's cheaper that writing letters. Wr ……此处隐藏3027个字……eat the sick, but they still can give off rays. Forthe normal people, they can be dangerous. So, we must think about this problem. As waste has four sorts, we can sort theminto each sort that they belong to. It’s convenient to treat them after they are sorted. Then we can deal with them sort bysort. We have thought out some methods like storing them in order to change them into plant food, or burning them in a hugestove and use the heat to make electricity. For the first way, the change rate is much too low and it may pollute the underground water. For the second one, of course it’s wonderful if it’s easy to be tried out. But to build such a huge stovewill cost too much. Not a good method. Now you see, treating waste is not an easy job.