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