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