I could bubble you could bubble she could bubble we could bubble you could bubble they could bubble
V-ing form
I could be bubbling you could be bubbling she could be bubbling we could be bubbling you could be bubbling they could be bubbling
Perfect
I could have bubbled you could have bubbled she could have bubbled we could have bubbled you could have bubbled they could have bubbled
V-ing perfect
I could have been bubbling you could have been bubbling she could have been bubbling we could have been bubbling you could have been bubbling they could have been bubbling
Negation
Simple form
I could not bubble you could not bubble she could not bubble we could not bubble you could not bubble they could not bubble
V-ing form
I could not be bubbling you could not be bubbling she could not be bubbling we could not be bubbling you could not be bubbling they could not be bubbling
Perfect
I could not have bubbled you could not have bubbled she could not have bubbled we could not have bubbled you could not have bubbled they could not have bubbled
V-ing perfect
I could not have been bubbling you could not have been bubbling she could not have been bubbling we could not have been bubbling you could not have been bubbling they could not have been bubbling
Interrogative form
Simple form
could I bubble? could you bubble? could she bubble? could we bubble? could you bubble? could they bubble?
V-ing form
could I be bubbling? could you be bubbling? could she be bubbling? could we be bubbling? could you be bubbling? could they be bubbling?
Perfect
could I have bubbled? could you have bubbled? could she have bubbled? could we have bubbled? could you have bubbled? could they have bubbled?
V-ing perfect
could I have been bubbling? could you have been bubbling? could she have been bubbling? could we have been bubbling? could you have been bubbling? could they have been bubbling?
Interro-negative form
Simple form
could I not bubble? could you not bubble? could she not bubble? could we not bubble? could you not bubble? could they not bubble?
V-ing form
could I not be bubbling? could you not be bubbling? could she not be bubbling? could we not be bubbling? could you not be bubbling? could they not be bubbling?
Perfect
could I not have bubbled? could you not have bubbled? could she not have bubbled? could we not have bubbled? could you not have bubbled? could they not have bubbled?
V-ing perfect
could I not have been bubbling? could you not have been bubbling? could she not have been bubbling? could we not have been bubbling? could you not have been bubbling? could they not have been bubbling?