要求进行句型转换，每空一词。
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)
___________________________________.
