I could bitter you could bitter she could bitter we could bitter you could bitter they could bitter
V-ing form
I could be bittering you could be bittering she could be bittering we could be bittering you could be bittering they could be bittering
Perfect
I could have bittered you could have bittered she could have bittered we could have bittered you could have bittered they could have bittered
V-ing perfect
I could have been bittering you could have been bittering she could have been bittering we could have been bittering you could have been bittering they could have been bittering
Negation
Simple form
I could not bitter you could not bitter she could not bitter we could not bitter you could not bitter they could not bitter
V-ing form
I could not be bittering you could not be bittering she could not be bittering we could not be bittering you could not be bittering they could not be bittering
Perfect
I could not have bittered you could not have bittered she could not have bittered we could not have bittered you could not have bittered they could not have bittered
V-ing perfect
I could not have been bittering you could not have been bittering she could not have been bittering we could not have been bittering you could not have been bittering they could not have been bittering
Interrogative form
Simple form
could I bitter? could you bitter? could she bitter? could we bitter? could you bitter? could they bitter?
V-ing form
could I be bittering? could you be bittering? could she be bittering? could we be bittering? could you be bittering? could they be bittering?
Perfect
could I have bittered? could you have bittered? could she have bittered? could we have bittered? could you have bittered? could they have bittered?
V-ing perfect
could I have been bittering? could you have been bittering? could she have been bittering? could we have been bittering? could you have been bittering? could they have been bittering?
Interro-negative form
Simple form
could I not bitter? could you not bitter? could she not bitter? could we not bitter? could you not bitter? could they not bitter?
V-ing form
could I not be bittering? could you not be bittering? could she not be bittering? could we not be bittering? could you not be bittering? could they not be bittering?
Perfect
could I not have bittered? could you not have bittered? could she not have bittered? could we not have bittered? could you not have bittered? could they not have bittered?
V-ing perfect
could I not have been bittering? could you not have been bittering? could she not have been bittering? could we not have been bittering? could you not have been bittering? could they not have been bittering?