原句与否定句对比
英语中，将肯定句变为否定句通常需要在 be 动词后加 not。
肯定句：That is a pen.
否定句：That is not a pen.
否定句：That is not a pen.
也可以使用缩写形式：That isn't a pen.
语法解析
- That：指示代词，意为“那个”
- is：be 动词的第三人称单数形式
- not：否定副词，用于构成否定句
- a pen：一个名词短语，表示“一支钢笔”
结构公式：主语 + be动词 + not + 表语
更多例句练习
This is a book. → This is not a book.
She is a teacher. → She is not a teacher.
It is my phone. → It is not my phone.
She is a teacher. → She is not a teacher.
It is my phone. → It is not my phone.
小测验（点击显示答案）
问题：如何将 “This is a cat.” 改为否定句？