I could volunteer you could volunteer he could volunteer we could volunteer you could volunteer they could volunteer
V-ing form
I could be volunteering you could be volunteering he could be volunteering we could be volunteering you could be volunteering they could be volunteering
Perfect
I could have volunteered you could have volunteered he could have volunteered we could have volunteered you could have volunteered they could have volunteered
V-ing perfect
I could have been volunteering you could have been volunteering he could have been volunteering we could have been volunteering you could have been volunteering they could have been volunteering
Negation
Simple form
I could not volunteer you could not volunteer he could not volunteer we could not volunteer you could not volunteer they could not volunteer
V-ing form
I could not be volunteering you could not be volunteering he could not be volunteering we could not be volunteering you could not be volunteering they could not be volunteering
Perfect
I could not have volunteered you could not have volunteered he could not have volunteered we could not have volunteered you could not have volunteered they could not have volunteered
V-ing perfect
I could not have been volunteering you could not have been volunteering he could not have been volunteering we could not have been volunteering you could not have been volunteering they could not have been volunteering
Interrogative form
Simple form
could I volunteer? could you volunteer? could he volunteer? could we volunteer? could you volunteer? could they volunteer?
V-ing form
could I be volunteering? could you be volunteering? could he be volunteering? could we be volunteering? could you be volunteering? could they be volunteering?
Perfect
could I have volunteered? could you have volunteered? could he have volunteered? could we have volunteered? could you have volunteered? could they have volunteered?
V-ing perfect
could I have been volunteering? could you have been volunteering? could he have been volunteering? could we have been volunteering? could you have been volunteering? could they have been volunteering?
Interro-negative form
Simple form
could I not volunteer? could you not volunteer? could he not volunteer? could we not volunteer? could you not volunteer? could they not volunteer?
V-ing form
could I not be volunteering? could you not be volunteering? could he not be volunteering? could we not be volunteering? could you not be volunteering? could they not be volunteering?
Perfect
could I not have volunteered? could you not have volunteered? could he not have volunteered? could we not have volunteered? could you not have volunteered? could they not have volunteered?
V-ing perfect
could I not have been volunteering? could you not have been volunteering? could he not have been volunteering? could we not have been volunteering? could you not have been volunteering? could they not have been volunteering?