I could grumble you could grumble she could grumble we could grumble you could grumble they could grumble
V-ing form
I could be grumbling you could be grumbling she could be grumbling we could be grumbling you could be grumbling they could be grumbling
Perfect
I could have grumbled you could have grumbled she could have grumbled we could have grumbled you could have grumbled they could have grumbled
V-ing perfect
I could have been grumbling you could have been grumbling she could have been grumbling we could have been grumbling you could have been grumbling they could have been grumbling
Negation
Simple form
I could not grumble you could not grumble she could not grumble we could not grumble you could not grumble they could not grumble
V-ing form
I could not be grumbling you could not be grumbling she could not be grumbling we could not be grumbling you could not be grumbling they could not be grumbling
Perfect
I could not have grumbled you could not have grumbled she could not have grumbled we could not have grumbled you could not have grumbled they could not have grumbled
V-ing perfect
I could not have been grumbling you could not have been grumbling she could not have been grumbling we could not have been grumbling you could not have been grumbling they could not have been grumbling
Interrogative form
Simple form
could I grumble? could you grumble? could she grumble? could we grumble? could you grumble? could they grumble?
V-ing form
could I be grumbling? could you be grumbling? could she be grumbling? could we be grumbling? could you be grumbling? could they be grumbling?
Perfect
could I have grumbled? could you have grumbled? could she have grumbled? could we have grumbled? could you have grumbled? could they have grumbled?
V-ing perfect
could I have been grumbling? could you have been grumbling? could she have been grumbling? could we have been grumbling? could you have been grumbling? could they have been grumbling?
Interro-negative form
Simple form
could I not grumble? could you not grumble? could she not grumble? could we not grumble? could you not grumble? could they not grumble?
V-ing form
could I not be grumbling? could you not be grumbling? could she not be grumbling? could we not be grumbling? could you not be grumbling? could they not be grumbling?
Perfect
could I not have grumbled? could you not have grumbled? could she not have grumbled? could we not have grumbled? could you not have grumbled? could they not have grumbled?
V-ing perfect
could I not have been grumbling? could you not have been grumbling? could she not have been grumbling? could we not have been grumbling? could you not have been grumbling? could they not have been grumbling?