I could bitter you could bitter he could bitter we could bitter you could bitter they could bitter
V-ing form
I could be bittering you could be bittering he could be bittering we could be bittering you could be bittering they could be bittering
Perfect
I could have bittered you could have bittered he 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 he could have been bittering we could have been bittering you could have been bittering they could have been bittering
Negation
Simple form
I couldn't bitter you couldn't bitter he couldn't bitter we couldn't bitter you couldn't bitter they couldn't bitter
V-ing form
I couldn't be bittering you couldn't be bittering he couldn't be bittering we couldn't be bittering you couldn't be bittering they couldn't be bittering
Perfect
I couldn't have bittered you couldn't have bittered he couldn't have bittered we couldn't have bittered you couldn't have bittered they couldn't have bittered
V-ing perfect
I couldn't have been bittering you couldn't have been bittering he couldn't have been bittering we couldn't have been bittering you couldn't have been bittering they couldn't have been bittering
Interrogative form
Simple form
could I bitter? could you bitter? could he bitter? could we bitter? could you bitter? could they bitter?
V-ing form
could I be bittering? could you be bittering? could he be bittering? could we be bittering? could you be bittering? could they be bittering?
Perfect
could I have bittered? could you have bittered? could he 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 he have been bittering? could we have been bittering? could you have been bittering? could they have been bittering?
Interro-negative form
Simple form
couldn't I bitter? couldn't you bitter? couldn't he bitter? couldn't we bitter? couldn't you bitter? couldn't they bitter?
V-ing form
couldn't I be bittering? couldn't you be bittering? couldn't he be bittering? couldn't we be bittering? couldn't you be bittering? couldn't they be bittering?
Perfect
couldn't I have bittered? couldn't you have bittered? couldn't he have bittered? couldn't we have bittered? couldn't you have bittered? couldn't they have bittered?
V-ing perfect
couldn't I have been bittering? couldn't you have been bittering? couldn't he have been bittering? couldn't we have been bittering? couldn't you have been bittering? couldn't they have been bittering?