could volunteer
Regular verb: volunteer - volunteered- volunteered

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could volunteer
you could volunteer
he could volunteer
we could volunteer
you could volunteer
they could volunteer 	I could be volunteering
you could be volunteering
he could be volunteering
we could be volunteering
you could be volunteering
they could be volunteering	I could have volunteered
you could have volunteered
he could have volunteered
we could have volunteered
you could have volunteered
they could have volunteered	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 	
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I couldn't volunteer
you couldn't volunteer
he couldn't volunteer
we couldn't volunteer
you couldn't volunteer
they couldn't volunteer 	I couldn't be volunteering
you couldn't be volunteering
he couldn't be volunteering
we couldn't be volunteering
you couldn't be volunteering
they couldn't be volunteering	I couldn't have volunteered
you couldn't have volunteered
he couldn't have volunteered
we couldn't have volunteered
you couldn't have volunteered
they couldn't have volunteered	I couldn't have been volunteering
you couldn't have been volunteering
he couldn't have been volunteering
we couldn't have been volunteering
you couldn't have been volunteering
they couldn't have been volunteering	

Interrogative form 	
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could I volunteer?
could you volunteer?
could he volunteer?
could we volunteer?
could you volunteer?
could they volunteer? 	could I be volunteering?
could you be volunteering?
could he be volunteering?
could we be volunteering?
could you be volunteering?
could they be volunteering? 	could I have volunteered?
could you have volunteered?
could he have volunteered?
could we have volunteered?
could you have volunteered?
could they have volunteered? 	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 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I volunteer?
couldn't you volunteer?
couldn't he volunteer?
couldn't we volunteer?
couldn't you volunteer?
couldn't they volunteer? 	couldn't I be volunteering?
couldn't you be volunteering?
couldn't he be volunteering?
couldn't we be volunteering?
couldn't you be volunteering?
couldn't they be volunteering? 	couldn't I have volunteered?
couldn't you have volunteered?
couldn't he have volunteered?
couldn't we have volunteered?
couldn't you have volunteered?
couldn't they have volunteered? 	couldn't I have been volunteering?
couldn't you have been volunteering?
couldn't he have been volunteering?
couldn't we have been volunteering?
couldn't you have been volunteering?
couldn't they have been volunteering?