I could telephone you could telephone he could telephone we could telephone you could telephone they could telephone
V-ing form
I could be telephoning you could be telephoning he could be telephoning we could be telephoning you could be telephoning they could be telephoning
Perfect
I could have telephoned you could have telephoned he could have telephoned we could have telephoned you could have telephoned they could have telephoned
V-ing perfect
I could have been telephoning you could have been telephoning he could have been telephoning we could have been telephoning you could have been telephoning they could have been telephoning
Negation
Simple form
I could not telephone you could not telephone he could not telephone we could not telephone you could not telephone they could not telephone
V-ing form
I could not be telephoning you could not be telephoning he could not be telephoning we could not be telephoning you could not be telephoning they could not be telephoning
Perfect
I could not have telephoned you could not have telephoned he could not have telephoned we could not have telephoned you could not have telephoned they could not have telephoned
V-ing perfect
I could not have been telephoning you could not have been telephoning he could not have been telephoning we could not have been telephoning you could not have been telephoning they could not have been telephoning
Interrogative form
Simple form
could I telephone? could you telephone? could he telephone? could we telephone? could you telephone? could they telephone?
V-ing form
could I be telephoning? could you be telephoning? could he be telephoning? could we be telephoning? could you be telephoning? could they be telephoning?
Perfect
could I have telephoned? could you have telephoned? could he have telephoned? could we have telephoned? could you have telephoned? could they have telephoned?
V-ing perfect
could I have been telephoning? could you have been telephoning? could he have been telephoning? could we have been telephoning? could you have been telephoning? could they have been telephoning?
Interro-negative form
Simple form
could I not telephone? could you not telephone? could he not telephone? could we not telephone? could you not telephone? could they not telephone?
V-ing form
could I not be telephoning? could you not be telephoning? could he not be telephoning? could we not be telephoning? could you not be telephoning? could they not be telephoning?
Perfect
could I not have telephoned? could you not have telephoned? could he not have telephoned? could we not have telephoned? could you not have telephoned? could they not have telephoned?
V-ing perfect
could I not have been telephoning? could you not have been telephoning? could he not have been telephoning? could we not have been telephoning? could you not have been telephoning? could they not have been telephoning?