2. 谓语动词的构成: 助动词be + V-ing。

请大家注意观察，其中的be 随着人称、数的变化而变化(am, is, are三种形式) 。

注: 不加助动词be的V.-ing 或 be+V原形不能构成现在进行时。如：

I’m visiting my friend. He is eating an ice cream. We’re preparing for Spring Festival. They are lying in the sun.

He visiting his friend. （×） He is visit his friend.（×）