英语上的书包怎么说怎么写

In Engpsh, a book bag is called a "backpack." You can write it as "backpack" or "book bag." Here are some sentences using these terms:

I always carry my backpack to school.
She packed her books into her book bag before heading out the door.
He left his backpack on the bus by accident.
I can't find my backpack anywhere!

Note that in American Engpsh, "book bag" is less common than "backpack," while in British Engpsh, "book bag" is more common.