I could worry you could worry he could worry we could worry you could worry they could worry
V-ing form
I could be worrying you could be worrying he could be worrying we could be worrying you could be worrying they could be worrying
Perfect
I could have worried you could have worried he 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 he could have been worrying we could have been worrying you could have been worrying they could have been worrying
Negation
Simple form
I could not worry you could not worry he could not worry we could not worry you could not worry they could not worry
V-ing form
I could not be worrying you could not be worrying he could not be worrying we could not be worrying you could not be worrying they could not be worrying
Perfect
I could not have worried you could not have worried he could not have worried we could not have worried you could not have worried they could not have worried
V-ing perfect
I could not have been worrying you could not have been worrying he could not have been worrying we could not have been worrying you could not have been worrying they could not have been worrying
Interrogative form
Simple form
could I worry? could you worry? could he worry? could we worry? could you worry? could they worry?
V-ing form
could I be worrying? could you be worrying? could he be worrying? could we be worrying? could you be worrying? could they be worrying?
Perfect
could I have worried? could you have worried? could he 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 he have been worrying? could we have been worrying? could you have been worrying? could they have been worrying?
Interro-negative form
Simple form
could I not worry? could you not worry? could he not worry? could we not worry? could you not worry? could they not worry?
V-ing form
could I not be worrying? could you not be worrying? could he not be worrying? could we not be worrying? could you not be worrying? could they not be worrying?
Perfect
could I not have worried? could you not have worried? could he not have worried? could we not have worried? could you not have worried? could they not have worried?
V-ing perfect
could I not have been worrying? could you not have been worrying? could he not have been worrying? could we not have been worrying? could you not have been worrying? could they not have been worrying?