一、be 的用法口诀 用am，你用are， is连着他/她/它——I am/You are /He is a student. 单数名词用is，复数名词全用are ——This is a book. / These are books. 变疑问，往前提，句末问号莫丟弃 ——Are you a student? 变否定，更容易，be后not莫忘记 ——I am not a student. 疑问否定任你变，句首大写莫迟疑 ——Are you/Is he a student?