must assist
Regular verb: assist - assisted- assisted

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must assist
you must assist
she must assist
we must assist
you must assist
they must assist 	I must be assisting
you must be assisting
she must be assisting
we must be assisting
you must be assisting
they must be assisting	I must have assisted
you must have assisted
she must have assisted
we must have assisted
you must have assisted
they must have assisted	I must have been assisting
you must have been assisting
she must have been assisting
we must have been assisting
you must have been assisting
they must have been assisting	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't assist
you mustn't assist
she mustn't assist
we mustn't assist
you mustn't assist
they mustn't assist 	I mustn't be assisting
you mustn't be assisting
she mustn't be assisting
we mustn't be assisting
you mustn't be assisting
they mustn't be assisting	I mustn't have assisted
you mustn't have assisted
she mustn't have assisted
we mustn't have assisted
you mustn't have assisted
they mustn't have assisted	I mustn't have been assisting
you mustn't have been assisting
she mustn't have been assisting
we mustn't have been assisting
you mustn't have been assisting
they mustn't have been assisting	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I assist?
must you assist?
must she assist?
must we assist?
must you assist?
must they assist? 	must I be assisting?
must you be assisting?
must she be assisting?
must we be assisting?
must you be assisting?
must they be assisting? 	must I have assisted?
must you have assisted?
must she have assisted?
must we have assisted?
must you have assisted?
must they have assisted? 	must I have been assisting?
must you have been assisting?
must she have been assisting?
must we have been assisting?
must you have been assisting?
must they have been assisting? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I assist?
mustn't you assist?
mustn't she assist?
mustn't we assist?
mustn't you assist?
mustn't they assist? 	mustn't I be assisting?
mustn't you be assisting?
mustn't she be assisting?
mustn't we be assisting?
mustn't you be assisting?
mustn't they be assisting? 	mustn't I have assisted?
mustn't you have assisted?
mustn't she have assisted?
mustn't we have assisted?
mustn't you have assisted?
mustn't they have assisted? 	mustn't I have been assisting?
mustn't you have been assisting?
mustn't she have been assisting?
mustn't we have been assisting?
mustn't you have been assisting?
mustn't they have been assisting?