I could grunt you could grunt she could grunt we could grunt you could grunt they could grunt
V-ing form
I could be grunting you could be grunting she could be grunting we could be grunting you could be grunting they could be grunting
Perfect
I could have grunted you could have grunted she could have grunted we could have grunted you could have grunted they could have grunted
V-ing perfect
I could have been grunting you could have been grunting she could have been grunting we could have been grunting you could have been grunting they could have been grunting
Negation
Simple form
I could not grunt you could not grunt she could not grunt we could not grunt you could not grunt they could not grunt
V-ing form
I could not be grunting you could not be grunting she could not be grunting we could not be grunting you could not be grunting they could not be grunting
Perfect
I could not have grunted you could not have grunted she could not have grunted we could not have grunted you could not have grunted they could not have grunted
V-ing perfect
I could not have been grunting you could not have been grunting she could not have been grunting we could not have been grunting you could not have been grunting they could not have been grunting
Interrogative form
Simple form
could I grunt? could you grunt? could she grunt? could we grunt? could you grunt? could they grunt?
V-ing form
could I be grunting? could you be grunting? could she be grunting? could we be grunting? could you be grunting? could they be grunting?
Perfect
could I have grunted? could you have grunted? could she have grunted? could we have grunted? could you have grunted? could they have grunted?
V-ing perfect
could I have been grunting? could you have been grunting? could she have been grunting? could we have been grunting? could you have been grunting? could they have been grunting?
Interro-negative form
Simple form
could I not grunt? could you not grunt? could she not grunt? could we not grunt? could you not grunt? could they not grunt?
V-ing form
could I not be grunting? could you not be grunting? could she not be grunting? could we not be grunting? could you not be grunting? could they not be grunting?
Perfect
could I not have grunted? could you not have grunted? could she not have grunted? could we not have grunted? could you not have grunted? could they not have grunted?
V-ing perfect
could I not have been grunting? could you not have been grunting? could she not have been grunting? could we not have been grunting? could you not have been grunting? could they not have been grunting?