1) This is a ball.The ball is blue.
2) There is a cosy sofa in my room. There are two nice pillows on the sofa.
3) It is a computer . Thecomputer is on the desk.
4) There is one big window in my room. There are many flowerpots on the windowsill.
5) There is a table with four chairs in the middle of my room the vase with flowers is on table.
1) a
2) a; the
3) a; the
4) the
5) a; the; the