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