must abstain
Regular verb: abstain - abstained- abstained

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must abstain
you must abstain
she must abstain
we must abstain
you must abstain
they must abstain 	I must be abstaining
you must be abstaining
she must be abstaining
we must be abstaining
you must be abstaining
they must be abstaining	I must have abstained
you must have abstained
she must have abstained
we must have abstained
you must have abstained
they must have abstained	I must have been abstaining
you must have been abstaining
she must have been abstaining
we must have been abstaining
you must have been abstaining
they must have been abstaining	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't abstain
you mustn't abstain
she mustn't abstain
we mustn't abstain
you mustn't abstain
they mustn't abstain 	I mustn't be abstaining
you mustn't be abstaining
she mustn't be abstaining
we mustn't be abstaining
you mustn't be abstaining
they mustn't be abstaining	I mustn't have abstained
you mustn't have abstained
she mustn't have abstained
we mustn't have abstained
you mustn't have abstained
they mustn't have abstained	I mustn't have been abstaining
you mustn't have been abstaining
she mustn't have been abstaining
we mustn't have been abstaining
you mustn't have been abstaining
they mustn't have been abstaining	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I abstain?
must you abstain?
must she abstain?
must we abstain?
must you abstain?
must they abstain? 	must I be abstaining?
must you be abstaining?
must she be abstaining?
must we be abstaining?
must you be abstaining?
must they be abstaining? 	must I have abstained?
must you have abstained?
must she have abstained?
must we have abstained?
must you have abstained?
must they have abstained? 	must I have been abstaining?
must you have been abstaining?
must she have been abstaining?
must we have been abstaining?
must you have been abstaining?
must they have been abstaining? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I abstain?
mustn't you abstain?
mustn't she abstain?
mustn't we abstain?
mustn't you abstain?
mustn't they abstain? 	mustn't I be abstaining?
mustn't you be abstaining?
mustn't she be abstaining?
mustn't we be abstaining?
mustn't you be abstaining?
mustn't they be abstaining? 	mustn't I have abstained?
mustn't you have abstained?
mustn't she have abstained?
mustn't we have abstained?
mustn't you have abstained?
mustn't they have abstained? 	mustn't I have been abstaining?
mustn't you have been abstaining?
mustn't she have been abstaining?
mustn't we have been abstaining?
mustn't you have been abstaining?
mustn't they have been abstaining?