I could grind you could grind she could grind we could grind you could grind they could grind
V-ing form
I could be grinding you could be grinding she could be grinding we could be grinding you could be grinding they could be grinding
Perfect
I could have ground you could have ground she 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 she could have been grinding we could have been grinding you could have been grinding they could have been grinding
Negation
Simple form
I couldn't grind you couldn't grind she couldn't grind we couldn't grind you couldn't grind they couldn't grind
V-ing form
I couldn't be grinding you couldn't be grinding she couldn't be grinding we couldn't be grinding you couldn't be grinding they couldn't be grinding
Perfect
I couldn't have ground you couldn't have ground she couldn't have ground we couldn't have ground you couldn't have ground they couldn't have ground
V-ing perfect
I couldn't have been grinding you couldn't have been grinding she couldn't have been grinding we couldn't have been grinding you couldn't have been grinding they couldn't have been grinding
Interrogative form
Simple form
could I grind? could you grind? could she grind? could we grind? could you grind? could they grind?
V-ing form
could I be grinding? could you be grinding? could she be grinding? could we be grinding? could you be grinding? could they be grinding?
Perfect
could I have ground? could you have ground? could she 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 she have been grinding? could we have been grinding? could you have been grinding? could they have been grinding?
Interro-negative form
Simple form
couldn't I grind? couldn't you grind? couldn't she grind? couldn't we grind? couldn't you grind? couldn't they grind?
V-ing form
couldn't I be grinding? couldn't you be grinding? couldn't she be grinding? couldn't we be grinding? couldn't you be grinding? couldn't they be grinding?
Perfect
couldn't I have ground? couldn't you have ground? couldn't she have ground? couldn't we have ground? couldn't you have ground? couldn't they have ground?
V-ing perfect
couldn't I have been grinding? couldn't you have been grinding? couldn't she have been grinding? couldn't we have been grinding? couldn't you have been grinding? couldn't they have been grinding?