COULD:
i could read when i was primary school.
i could play piano when i was primary school.
i could ride a bike when i was primary school.
COULDN'T:
i couldn't play violon when i was primary school.
i couldn't take with the British.
i couldn't play chess when i was primary school.
- I could play badminton when i were young.
- I could swim very well at the age of 8.
- I could read and write at the age of 6.
- I couldn't understand English in conversations when i were 7.
- I could't write a letter to an English friend when i am in year 8.
- I couldn't climb the trees when i am in year 10.