I could grind you could grind he could grind we could grind you could grind they could grind
V-ing form
I could be grinding you could be grinding he could be grinding we could be grinding you could be grinding they could be grinding
Perfect
I could have ground you could have ground he could have ground we could have ground you could have ground they could have ground
V-ing perfect
I could have been grinding you could have been grinding he could have been grinding we could have been grinding you could have been grinding they could have been grinding
Negation
Simple form
I could not grind you could not grind he could not grind we could not grind you could not grind they could not grind
V-ing form
I could not be grinding you could not be grinding he could not be grinding we could not be grinding you could not be grinding they could not be grinding
Perfect
I could not have ground you could not have ground he could not have ground we could not have ground you could not have ground they could not have ground
V-ing perfect
I could not have been grinding you could not have been grinding he could not have been grinding we could not have been grinding you could not have been grinding they could not have been grinding
Interrogative form
Simple form
could I grind? could you grind? could he grind? could we grind? could you grind? could they grind?
V-ing form
could I be grinding? could you be grinding? could he be grinding? could we be grinding? could you be grinding? could they be grinding?
Perfect
could I have ground? could you have ground? could he have ground? could we have ground? could you have ground? could they have ground?
V-ing perfect
could I have been grinding? could you have been grinding? could he have been grinding? could we have been grinding? could you have been grinding? could they have been grinding?
Interro-negative form
Simple form
could I not grind? could you not grind? could he not grind? could we not grind? could you not grind? could they not grind?
V-ing form
could I not be grinding? could you not be grinding? could he not be grinding? could we not be grinding? could you not be grinding? could they not be grinding?
Perfect
could I not have ground? could you not have ground? could he not have ground? could we not have ground? could you not have ground? could they not have ground?
V-ing perfect
could I not have been grinding? could you not have been grinding? could he not have been grinding? could we not have been grinding? could you not have been grinding? could they not have been grinding?