b动词第一人称单数是什么

be动词第一人称单数用am。

如：I am a girl..

第二人称单复数和人称复数用are。

如：We are young. You（你）are smart. You（你们）are kindness. They are strong.

第三人称单数用is。

如：It is a rabbit. She is beautiful. He is tall.