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