could smooth
Regular verb: smooth - smoothed- smoothed

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could smooth
you could smooth
he could smooth
we could smooth
you could smooth
they could smooth 	I could be smoothing
you could be smoothing
he could be smoothing
we could be smoothing
you could be smoothing
they could be smoothing	I could have smoothed
you could have smoothed
he could have smoothed
we could have smoothed
you could have smoothed
they could have smoothed	I could have been smoothing
you could have been smoothing
he could have been smoothing
we could have been smoothing
you could have been smoothing
they could have been smoothing	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't smooth
you couldn't smooth
he couldn't smooth
we couldn't smooth
you couldn't smooth
they couldn't smooth 	I couldn't be smoothing
you couldn't be smoothing
he couldn't be smoothing
we couldn't be smoothing
you couldn't be smoothing
they couldn't be smoothing	I couldn't have smoothed
you couldn't have smoothed
he couldn't have smoothed
we couldn't have smoothed
you couldn't have smoothed
they couldn't have smoothed	I couldn't have been smoothing
you couldn't have been smoothing
he couldn't have been smoothing
we couldn't have been smoothing
you couldn't have been smoothing
they couldn't have been smoothing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I smooth?
could you smooth?
could he smooth?
could we smooth?
could you smooth?
could they smooth? 	could I be smoothing?
could you be smoothing?
could he be smoothing?
could we be smoothing?
could you be smoothing?
could they be smoothing? 	could I have smoothed?
could you have smoothed?
could he have smoothed?
could we have smoothed?
could you have smoothed?
could they have smoothed? 	could I have been smoothing?
could you have been smoothing?
could he have been smoothing?
could we have been smoothing?
could you have been smoothing?
could they have been smoothing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I smooth?
couldn't you smooth?
couldn't he smooth?
couldn't we smooth?
couldn't you smooth?
couldn't they smooth? 	couldn't I be smoothing?
couldn't you be smoothing?
couldn't he be smoothing?
couldn't we be smoothing?
couldn't you be smoothing?
couldn't they be smoothing? 	couldn't I have smoothed?
couldn't you have smoothed?
couldn't he have smoothed?
couldn't we have smoothed?
couldn't you have smoothed?
couldn't they have smoothed? 	couldn't I have been smoothing?
couldn't you have been smoothing?
couldn't he have been smoothing?
couldn't we have been smoothing?
couldn't you have been smoothing?
couldn't they have been smoothing?