must sharpen
Regular verb: sharpen - sharpened- sharpened

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

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

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

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