科技
人称代词：
I am a student.
You are a teacher.
He is a worker.
She has a dog.
They will go to Beijing.
指示代词：
This is Mary.
That is my coat.
疑问代词：
what is this?
不定代词：
Both of them are teachers.
some (of them) are doctors,some (of them) are nurse.
