I could worry you could worry she could worry we could worry you could worry they could worry
V-ing form
I could be worrying you could be worrying she could be worrying we could be worrying you could be worrying they could be worrying
Perfect
I could have worried you could have worried she could have worried we could have worried you could have worried they could have worried
V-ing perfect
I could have been worrying you could have been worrying she could have been worrying we could have been worrying you could have been worrying they could have been worrying
Negation
Simple form
I couldn't worry you couldn't worry she couldn't worry we couldn't worry you couldn't worry they couldn't worry
V-ing form
I couldn't be worrying you couldn't be worrying she couldn't be worrying we couldn't be worrying you couldn't be worrying they couldn't be worrying
Perfect
I couldn't have worried you couldn't have worried she couldn't have worried we couldn't have worried you couldn't have worried they couldn't have worried
V-ing perfect
I couldn't have been worrying you couldn't have been worrying she couldn't have been worrying we couldn't have been worrying you couldn't have been worrying they couldn't have been worrying
Interrogative form
Simple form
could I worry? could you worry? could she worry? could we worry? could you worry? could they worry?
V-ing form
could I be worrying? could you be worrying? could she be worrying? could we be worrying? could you be worrying? could they be worrying?
Perfect
could I have worried? could you have worried? could she have worried? could we have worried? could you have worried? could they have worried?
V-ing perfect
could I have been worrying? could you have been worrying? could she have been worrying? could we have been worrying? could you have been worrying? could they have been worrying?
Interro-negative form
Simple form
couldn't I worry? couldn't you worry? couldn't she worry? couldn't we worry? couldn't you worry? couldn't they worry?
V-ing form
couldn't I be worrying? couldn't you be worrying? couldn't she be worrying? couldn't we be worrying? couldn't you be worrying? couldn't they be worrying?
Perfect
couldn't I have worried? couldn't you have worried? couldn't she have worried? couldn't we have worried? couldn't you have worried? couldn't they have worried?
V-ing perfect
couldn't I have been worrying? couldn't you have been worrying? couldn't she have been worrying? couldn't we have been worrying? couldn't you have been worrying? couldn't they have been worrying?