must whistle
Regular verb: whistle - whistled- whistled

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must whistle
you must whistle
she must whistle
we must whistle
you must whistle
they must whistle 	I must be whistling
you must be whistling
she must be whistling
we must be whistling
you must be whistling
they must be whistling	I must have whistled
you must have whistled
she must have whistled
we must have whistled
you must have whistled
they must have whistled	I must have been whistling
you must have been whistling
she must have been whistling
we must have been whistling
you must have been whistling
they must have been whistling	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't whistle
you mustn't whistle
she mustn't whistle
we mustn't whistle
you mustn't whistle
they mustn't whistle 	I mustn't be whistling
you mustn't be whistling
she mustn't be whistling
we mustn't be whistling
you mustn't be whistling
they mustn't be whistling	I mustn't have whistled
you mustn't have whistled
she mustn't have whistled
we mustn't have whistled
you mustn't have whistled
they mustn't have whistled	I mustn't have been whistling
you mustn't have been whistling
she mustn't have been whistling
we mustn't have been whistling
you mustn't have been whistling
they mustn't have been whistling	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I whistle?
must you whistle?
must she whistle?
must we whistle?
must you whistle?
must they whistle? 	must I be whistling?
must you be whistling?
must she be whistling?
must we be whistling?
must you be whistling?
must they be whistling? 	must I have whistled?
must you have whistled?
must she have whistled?
must we have whistled?
must you have whistled?
must they have whistled? 	must I have been whistling?
must you have been whistling?
must she have been whistling?
must we have been whistling?
must you have been whistling?
must they have been whistling? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I whistle?
mustn't you whistle?
mustn't she whistle?
mustn't we whistle?
mustn't you whistle?
mustn't they whistle? 	mustn't I be whistling?
mustn't you be whistling?
mustn't she be whistling?
mustn't we be whistling?
mustn't you be whistling?
mustn't they be whistling? 	mustn't I have whistled?
mustn't you have whistled?
mustn't she have whistled?
mustn't we have whistled?
mustn't you have whistled?
mustn't they have whistled? 	mustn't I have been whistling?
mustn't you have been whistling?
mustn't she have been whistling?
mustn't we have been whistling?
mustn't you have been whistling?
mustn't they have been whistling?