Can and can't have the same form in all persons.
There is no do or does.
Can is followed by the infinitive (without to).
She can swim.He can't dance. NOTWas / Were is the past of am / is / are.
| Subject | ||
|---|---|---|
| I / He / She / It | was | in Paris yesterday. |
| We / You / They | were | in England last year. |
| Subject | ||
|---|---|---|
| I / He / She / It | wasn't | at school yesterday. |
| We / You / They | weren't | at the party last night. |
Could is the past of can.
Could and couldn't have the same form in all persons.
Could is followed by the infinitive (without to).
| Subject | ||
|---|---|---|
| I / He / She / It / We / You / They | could | swim. |
| Subject | ||
|---|---|---|
| I / He / She / It / We / You / They | couldn't | dance. |
| Q. word | Auxiliary | Subject | Verb |
|---|---|---|---|
| What | could | I / he/she/it / we/you/they | do? |
| To be | Subject | Short answers | |
|---|---|---|---|
| Could | you / she / they / etc. | drive? / cook? | Yes, she could. / Yes, they could. / No, we couldn't. |