a / an
1. This is egg.
2. It is bus.
3. That is ruler.
4. It is apple.
5. This is house.
6. It is cat.
7. That is girl.
8. It is umbrella.
9. That is kite.
10. This is dog.
11. This is orange.
12. That is car.
13. This is van.
14. It is ant.
15. It is fan.
16. It is ice-cream.