陈述句（肯定、否定）：He is six years old.She didn’t hear of you before.
2）疑问句（一般、特殊、选择、反意）：Do they like skating?How old is he?Is he six or seven years old?Mary can swim,can’t she?
3）祈使句：Be careful,boys; Don’t talk in class
4）感叹句：How clever the boy is!