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