1. I'm not sad. I'm happy. 

2. Ice isn't hot. It is cold. 

3. Mr. Thomas isn't rich. He is poor. 

4. My hair isn't long. It is short. 

5. My clothes aren't dirty. They are clean. 

6. Flowers aren't ugly. They are beautiful. 

7. Cars aren't cheap. They are expensive. 

8. Airplanes aren't slow. They are fast. 

9. Grammar isn't difficult. It is easy. 

10. My sister isn't short. She is tall. 

11. My grandparents aren't young. They are old. 

12. The dormitory isn't quiet. It is loud. 

13. The door isn't closed. It is open. 

14. Guns aren't safe. They are dangerous. 

15. Lemon's aren't sweet. They are sour.