I could mumble you could mumble she could mumble we could mumble you could mumble they could mumble
V-ing form
I could be mumbling you could be mumbling she could be mumbling we could be mumbling you could be mumbling they could be mumbling
Perfect
I could have mumbled you could have mumbled she could have mumbled we could have mumbled you could have mumbled they could have mumbled
V-ing perfect
I could have been mumbling you could have been mumbling she could have been mumbling we could have been mumbling you could have been mumbling they could have been mumbling
Negation
Simple form
I could not mumble you could not mumble she could not mumble we could not mumble you could not mumble they could not mumble
V-ing form
I could not be mumbling you could not be mumbling she could not be mumbling we could not be mumbling you could not be mumbling they could not be mumbling
Perfect
I could not have mumbled you could not have mumbled she could not have mumbled we could not have mumbled you could not have mumbled they could not have mumbled
V-ing perfect
I could not have been mumbling you could not have been mumbling she could not have been mumbling we could not have been mumbling you could not have been mumbling they could not have been mumbling
Interrogative form
Simple form
could I mumble? could you mumble? could she mumble? could we mumble? could you mumble? could they mumble?
V-ing form
could I be mumbling? could you be mumbling? could she be mumbling? could we be mumbling? could you be mumbling? could they be mumbling?
Perfect
could I have mumbled? could you have mumbled? could she have mumbled? could we have mumbled? could you have mumbled? could they have mumbled?
V-ing perfect
could I have been mumbling? could you have been mumbling? could she have been mumbling? could we have been mumbling? could you have been mumbling? could they have been mumbling?
Interro-negative form
Simple form
could I not mumble? could you not mumble? could she not mumble? could we not mumble? could you not mumble? could they not mumble?
V-ing form
could I not be mumbling? could you not be mumbling? could she not be mumbling? could we not be mumbling? could you not be mumbling? could they not be mumbling?
Perfect
could I not have mumbled? could you not have mumbled? could she not have mumbled? could we not have mumbled? could you not have mumbled? could they not have mumbled?
V-ing perfect
could I not have been mumbling? could you not have been mumbling? could she not have been mumbling? could we not have been mumbling? could you not have been mumbling? could they not have been mumbling?