1. Those are pictures.   (改为单数句)
That's ______ _______.
2. This is an apple tree.  (改为复数句)
These _____ _____ ____.
3. There are some pictures on the wall.   (变为一般疑问句)
______ ______ _____ pictures on the wall?
4. There are some dictionaries in the library.  (变为否定句)
There _____ ______ dictionaries in the library.
5. There is a computer in the classroom.   There are two blackboards in the classroom.(把两句合为一句)

___________________________________.