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