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