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