I could collaborate you could collaborate she could collaborate we could collaborate you could collaborate they could collaborate
V-ing form
I could be collaborating you could be collaborating she could be collaborating we could be collaborating you could be collaborating they could be collaborating
Perfect
I could have collaborated you could have collaborated she 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 she 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 she 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 she 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 she 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 she 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 she collaborate? could we collaborate? could you collaborate? could they collaborate?
V-ing form
could I be collaborating? could you be collaborating? could she be collaborating? could we be collaborating? could you be collaborating? could they be collaborating?
Perfect
could I have collaborated? could you have collaborated? could she 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 she 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 she 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 she 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 she 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 she have been collaborating? couldn't we have been collaborating? couldn't you have been collaborating? couldn't they have been collaborating?