must thumb
Regular verb: thumb - thumbed- thumbed

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must thumb
you must thumb
she must thumb
we must thumb
you must thumb
they must thumb 	I must be thumbing
you must be thumbing
she must be thumbing
we must be thumbing
you must be thumbing
they must be thumbing	I must have thumbed
you must have thumbed
she must have thumbed
we must have thumbed
you must have thumbed
they must have thumbed	I must have been thumbing
you must have been thumbing
she must have been thumbing
we must have been thumbing
you must have been thumbing
they must have been thumbing	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't thumb
you mustn't thumb
she mustn't thumb
we mustn't thumb
you mustn't thumb
they mustn't thumb 	I mustn't be thumbing
you mustn't be thumbing
she mustn't be thumbing
we mustn't be thumbing
you mustn't be thumbing
they mustn't be thumbing	I mustn't have thumbed
you mustn't have thumbed
she mustn't have thumbed
we mustn't have thumbed
you mustn't have thumbed
they mustn't have thumbed	I mustn't have been thumbing
you mustn't have been thumbing
she mustn't have been thumbing
we mustn't have been thumbing
you mustn't have been thumbing
they mustn't have been thumbing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I thumb?
must you thumb?
must she thumb?
must we thumb?
must you thumb?
must they thumb? 	must I be thumbing?
must you be thumbing?
must she be thumbing?
must we be thumbing?
must you be thumbing?
must they be thumbing? 	must I have thumbed?
must you have thumbed?
must she have thumbed?
must we have thumbed?
must you have thumbed?
must they have thumbed? 	must I have been thumbing?
must you have been thumbing?
must she have been thumbing?
must we have been thumbing?
must you have been thumbing?
must they have been thumbing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I thumb?
mustn't you thumb?
mustn't she thumb?
mustn't we thumb?
mustn't you thumb?
mustn't they thumb? 	mustn't I be thumbing?
mustn't you be thumbing?
mustn't she be thumbing?
mustn't we be thumbing?
mustn't you be thumbing?
mustn't they be thumbing? 	mustn't I have thumbed?
mustn't you have thumbed?
mustn't she have thumbed?
mustn't we have thumbed?
mustn't you have thumbed?
mustn't they have thumbed? 	mustn't I have been thumbing?
mustn't you have been thumbing?
mustn't she have been thumbing?
mustn't we have been thumbing?
mustn't you have been thumbing?
mustn't they have been thumbing?