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