1. I can play chess very well.
2. My grandfather could play chess very well too, but now he's dead.
3. I think my grandchildren will be able to play chess when they grow up.
4. I must come home at 6 o'clock, or else my mom yells at me.
5. I had to come home at 5 o'clock one time because she was too worried about me.
6. I will have to come home at 6 o'clock for the rest of my life.
7. I can't swim in salty water.
8. Probably because that one time my father had thrown me in the sea and I couldn't swim out.
9. Because of those traumatic memories, I will never be able to swim in salty water.
10. I must go to school every day.
11. I didn't have to go to school when I was youger.
12. But now that I'm older, I will have to go to school until I'm eighteen.
