There __________ three books.
are
There __________ a backpack.
is
There __________ three chairs.
are
Is there a ruler in the classroom?
No, there isn't. There are two.
There __________ a computer.
isn't.
There ___________ two erasers.
are
There __________ four students.
are
Are there four pencils in the classroom?
Yes, there are.
There __________ a teacher.
is