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