请问什么是一般现在时，它的句形是什么？

动词一般现在时的句型结构分为三种：连系动词be，动词have和其他行为动词

1． 联系动词be（又称be动词）一般现在时的句型：连系动词be要随主语的人称和数变为am, are, is。第一人称单数用am, 第二人称单数用are, 第三人称单数用is，各人称复数一律用are.

2． 肯定句型：主语＋be+表语

单数 复数

I am a student. We are students.

You are a doctor. You are doctors.

He is tall. They are tall.

She is a teacher. They are new.

It is nice today.

3． 否定句型：主语＋be+not+表语。（只在be后面加not）

单数

I am not a student. We are not students.

You are not a doctor. You are not doctors.

He is not tall. They are not tall.

She is not a teacher. They are not new.

4． 疑问句型：Be＋主语＋表语？（将be置于主语前面）