肯定句变否定句1. 简单句中含有系动词be情态动词和助动词时变否定句时需在系动词be情态动词和助动词后加not如: I am a teacher.→I am not a teacher. He can help me.→He cant help me. 2.简单句中谓语动词为行为动词时要根据时态选用do的相应形式把肯定句变为否定句如: The little girl wants to