英语句子中,怎么区分主语、be 动词?

主语一般是人（例如Jane)、物(book)或物主代词(she),谓语是动词,谓语后面的就是宾语.
be动词包括am,is,are
Jane is a student.(She is a student.)
I am a student.
They are students.
The book is on the desk.
The books are on the desk