could quiver
Regular verb: quiver - quivered- quivered

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could quiver
you could quiver
he could quiver
we could quiver
you could quiver
they could quiver 	I could be quivering
you could be quivering
he could be quivering
we could be quivering
you could be quivering
they could be quivering	I could have quivered
you could have quivered
he could have quivered
we could have quivered
you could have quivered
they could have quivered	I could have been quivering
you could have been quivering
he could have been quivering
we could have been quivering
you could have been quivering
they could have been quivering	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't quiver
you couldn't quiver
he couldn't quiver
we couldn't quiver
you couldn't quiver
they couldn't quiver 	I couldn't be quivering
you couldn't be quivering
he couldn't be quivering
we couldn't be quivering
you couldn't be quivering
they couldn't be quivering	I couldn't have quivered
you couldn't have quivered
he couldn't have quivered
we couldn't have quivered
you couldn't have quivered
they couldn't have quivered	I couldn't have been quivering
you couldn't have been quivering
he couldn't have been quivering
we couldn't have been quivering
you couldn't have been quivering
they couldn't have been quivering	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I quiver?
could you quiver?
could he quiver?
could we quiver?
could you quiver?
could they quiver? 	could I be quivering?
could you be quivering?
could he be quivering?
could we be quivering?
could you be quivering?
could they be quivering? 	could I have quivered?
could you have quivered?
could he have quivered?
could we have quivered?
could you have quivered?
could they have quivered? 	could I have been quivering?
could you have been quivering?
could he have been quivering?
could we have been quivering?
could you have been quivering?
could they have been quivering? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I quiver?
couldn't you quiver?
couldn't he quiver?
couldn't we quiver?
couldn't you quiver?
couldn't they quiver? 	couldn't I be quivering?
couldn't you be quivering?
couldn't he be quivering?
couldn't we be quivering?
couldn't you be quivering?
couldn't they be quivering? 	couldn't I have quivered?
couldn't you have quivered?
couldn't he have quivered?
couldn't we have quivered?
couldn't you have quivered?
couldn't they have quivered? 	couldn't I have been quivering?
couldn't you have been quivering?
couldn't he have been quivering?
couldn't we have been quivering?
couldn't you have been quivering?
couldn't they have been quivering?