Is there a cup here?
Yes, there is one.
Yes, it is.

Are there twenty pencils in this box?
Yes, there are ten.
Yes, there are.

Is there a computer in the library?
Yes, you are not.
Yes, there is one.

Is there a dog in this house?
Yes, there is a dog.
Yes, there are two houses.

Are there four books on the desk?
Yes, you are.
Yes, there are.

Are there twenty cigarettes in this packet?
Yes, there are.
Yes, there is.

Is there a book about computers in the library?
Yes, there is one.
Yes, there are one.

Are there three rabbits in the garden?
No, there isn't three rabbits.
No, there aren't three rabbits.