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