一般现在时：表示一般性，经常性的动作或一般性事实
含有be动词的句子
He is a teacher.
The girl is very beautiful.
Tim and Jack are students.
变疑问句将be动词移到句首
Is he a teacher?
Is the girl very beautiful?
Are Tim and Jack students?
变否定句在be动词后面加not
He is not a teacher.
The girl is not very beautiful.
Tim and Jack are not students.
肯定回答及否定回答
Yes, he is. No, he is not.
Yes, she is. No, she is not.
Yes, they are. No, they are not.
不含有动词的句子，即含有一般动词的句子
第三人称单数及单数名词
He likes books.
She likes him.
The dog likes bones.
变疑问句在句首加does, 动词变为原型
Does he like books?
Does she like him?
Does the dog like bones?
变否定句在主语及动词之间加doesn’t, 动词变为原型
He doesn’t like books.
She doesn’t like him.
The dog doesn’t like bones.
