must riff
Regular verb: riff - riffed- riffed

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must riff
you must riff
she must riff
we must riff
you must riff
they must riff 	I must be riffing
you must be riffing
she must be riffing
we must be riffing
you must be riffing
they must be riffing	I must have riffed
you must have riffed
she must have riffed
we must have riffed
you must have riffed
they must have riffed	I must have been riffing
you must have been riffing
she must have been riffing
we must have been riffing
you must have been riffing
they must have been riffing	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must not riff
you must not riff
she must not riff
we must not riff
you must not riff
they must not riff 	I must not be riffing
you must not be riffing
she must not be riffing
we must not be riffing
you must not be riffing
they must not be riffing	I must not have riffed
you must not have riffed
she must not have riffed
we must not have riffed
you must not have riffed
they must not have riffed	I must not have been riffing
you must not have been riffing
she must not have been riffing
we must not have been riffing
you must not have been riffing
they must not have been riffing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I riff?
must you riff?
must she riff?
must we riff?
must you riff?
must they riff? 	must I be riffing?
must you be riffing?
must she be riffing?
must we be riffing?
must you be riffing?
must they be riffing? 	must I have riffed?
must you have riffed?
must she have riffed?
must we have riffed?
must you have riffed?
must they have riffed? 	must I have been riffing?
must you have been riffing?
must she have been riffing?
must we have been riffing?
must you have been riffing?
must they have been riffing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I not riff?
must you not riff?
must she not riff?
must we not riff?
must you not riff?
must they not riff? 	must I not be riffing?
must you not be riffing?
must she not be riffing?
must we not be riffing?
must you not be riffing?
must they not be riffing? 	must I not have riffed?
must you not have riffed?
must she not have riffed?
must we not have riffed?
must you not have riffed?
must they not have riffed? 	must I not have been riffing?
must you not have been riffing?
must she not have been riffing?
must we not have been riffing?
must you not have been riffing?
must they not have been riffing?