雅思写作中，学生们逗号用法的错误是层出不穷。其中最让人印象深刻的是"一逗到底"的现象。为了让大家今后使用逗号时做到胸有成竹，今天就来介绍逗号的四种用法：introducer commas, coordinator commas, inserter commas, and tag commas. 学完后，相信大家一定会有所收获。

　　1. Introducer Commas（引入君逗号）

　　在第一个独立小句前出现的成分之后，使用逗号。例如，

　　Therefore, I plan to quit smoking. （副词之后）

　　After 16 years of smoking, it is not easy to quit. （词组之后）

　　Because I have a chronic cough, my doctor recommended that I quit immediately. （从句之后）

　　"Stop smoking today, " she advised. （直接引语之后）

　　2. Coordinator Commas（连词君逗号）

　　与并列连词搭配使用，用于连接句中并列的成分。例如，

　　She has a good job, yet she is always broke. （两个独立小句）

　　He does not enjoy skiing, ice-skating, or sledding. （三个并列单词）

　　A nurse has to work at night, on weekends, and on holidays. （三个并列词组）

　　3. Inserter Commas（插入君逗号）

　　独立小句中的插入语前后均使用逗号。例如，

　　My uncle, however, refuses to quit smoking. （副词前后）

　　My father, on the other hand, has never smoked. （词组前后）

　　My mother , who just celebrated her fiftieth birthday, enjoys an occasional cigarette. （非限制性从句前后）

　　4. Tag Commas（标签君逗号）

　　当增加某些成分在句尾时，在该成分前使用逗号。例如，

　　My uncle believes in drinking a daily glass of wine, too. （单词之前）

　　He swims for an hour every day, for example. （词组之前）

　　He also plays tennis, beating me most of the time. （词组之前）

　　这四种用法，同学们都学会了吗？接下来就是检验的时刻了！

　　给下面句子在必要的地方加上逗号，并指出其具体用法。

　　1. The advertising industry which is one of the largest industries in the United States employs millions of people and spends billions of dollars.

　　2. Every minute of the day and night people are exposed to ads on television on billboards in the newspapers and in magazines.

　　3. Sex is used in many cigarette and liquor ads for example.

　　4. Advertising is essential to the free enterprise system yet it can sometimes be very annoying.

（未完待续）