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