文中共有10处语言错误，每句中最多有两处。错误涉及一个单词的增加、删除或修改。
增加：在缺词处加一个漏字符号（∧），并在其下面写出该加的词。
删除：多余的词用斜线（\）划掉。
修改：在错的词下划一横线，并在该词下面写出修改后的词。
注意：1.每处错误及其修改均仅限一词；
2.只允许修改10处，多者（从第11处起）不计分。
Many young boys and girls had the habit of smoking, though they are middle school student. As we all know, smoking does harm for human beings. More and more people have realized that how serious this problem is. But they are never boring with it. Some people think smoking is a kind of fashion, and others think smoking can refresh himself. In fact, smoking cause many illnesses. The most serious illness caused of smoking is lung cancer. Meanwhile, smoking is the waste of money. What’s worse, careless smokers may cause danger fires.