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