I. could
She could swim when she was five.
If you tried, you could do that work.
His story could be true, but I hardly think it is.
I could do the job today, but I’d rather put it off until tomorrow.
My grandfather could speak five languages
II.couldn't
He hurt his foot, and he couldn’t play in the match.
The door was locked, and I couldn’t open it.
In the past, robots couldn't talk to humans.
She couldn't walk because she pain her legs.
I couldn't speak Chinese.
III.can
In London buses you can smoke on the upper deck, but you can’t smoke downstairs.
I can look after younger brother for parents.
I can sing
He can eat
She can dance
IV.was able to
I finished my work early and so was able to go to the pub with my friends.
The fire spread through the building quickly but everybody was able to escape or … everybody managed to escape (but not ‘could escape’)
The fire spread through the building quickly but everybody was able to escape or … everybody managed to escape (but not ‘could escape’)
Please arrive early so that we were able to start the meeting on time
V. will be able to
I will be able to learn English well in the future
They will be able to build a structure next year.
The baby will be able to speak next month.
Robot will be albe to do housework in the future
Robot will be able to teaching people
VI. is/are/ am able to
The children are able to sing.
The boy is able to swim when he was 6 years old.
