Ability- can- could; 1)I can learn English; 2)I can do this work for 2 hours

Obligity – to be able to; 1) I am able to wash my dad’ s car.

probability- may;might; 1)May I come late. 2) I might get up late, but I’ll be at school on time.

Have to- had to 1) I have to learn better 2) She had to call me.