could sharpen
Regular verb: sharpen - sharpened- sharpened

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could sharpen
you could sharpen
he could sharpen
we could sharpen
you could sharpen
they could sharpen 	I could be sharpening
you could be sharpening
he could be sharpening
we could be sharpening
you could be sharpening
they could be sharpening	I could have sharpened
you could have sharpened
he could have sharpened
we could have sharpened
you could have sharpened
they could have sharpened	I could have been sharpening
you could have been sharpening
he could have been sharpening
we could have been sharpening
you could have been sharpening
they could have been sharpening	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't sharpen
you couldn't sharpen
he couldn't sharpen
we couldn't sharpen
you couldn't sharpen
they couldn't sharpen 	I couldn't be sharpening
you couldn't be sharpening
he couldn't be sharpening
we couldn't be sharpening
you couldn't be sharpening
they couldn't be sharpening	I couldn't have sharpened
you couldn't have sharpened
he couldn't have sharpened
we couldn't have sharpened
you couldn't have sharpened
they couldn't have sharpened	I couldn't have been sharpening
you couldn't have been sharpening
he couldn't have been sharpening
we couldn't have been sharpening
you couldn't have been sharpening
they couldn't have been sharpening	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I sharpen?
could you sharpen?
could he sharpen?
could we sharpen?
could you sharpen?
could they sharpen? 	could I be sharpening?
could you be sharpening?
could he be sharpening?
could we be sharpening?
could you be sharpening?
could they be sharpening? 	could I have sharpened?
could you have sharpened?
could he have sharpened?
could we have sharpened?
could you have sharpened?
could they have sharpened? 	could I have been sharpening?
could you have been sharpening?
could he have been sharpening?
could we have been sharpening?
could you have been sharpening?
could they have been sharpening? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I sharpen?
couldn't you sharpen?
couldn't he sharpen?
couldn't we sharpen?
couldn't you sharpen?
couldn't they sharpen? 	couldn't I be sharpening?
couldn't you be sharpening?
couldn't he be sharpening?
couldn't we be sharpening?
couldn't you be sharpening?
couldn't they be sharpening? 	couldn't I have sharpened?
couldn't you have sharpened?
couldn't he have sharpened?
couldn't we have sharpened?
couldn't you have sharpened?
couldn't they have sharpened? 	couldn't I have been sharpening?
couldn't you have been sharpening?
couldn't he have been sharpening?
couldn't we have been sharpening?
couldn't you have been sharpening?
couldn't they have been sharpening?