must thumb
Regular verb: thumb - thumbed- thumbed

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must thumb
you must thumb
he must thumb
we must thumb
you must thumb
they must thumb 	I must be thumbing
you must be thumbing
he must be thumbing
we must be thumbing
you must be thumbing
they must be thumbing	I must have thumbed
you must have thumbed
he 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
he 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 must not thumb
you must not thumb
he must not thumb
we must not thumb
you must not thumb
they must not thumb 	I must not be thumbing
you must not be thumbing
he must not be thumbing
we must not be thumbing
you must not be thumbing
they must not be thumbing	I must not have thumbed
you must not have thumbed
he must not have thumbed
we must not have thumbed
you must not have thumbed
they must not have thumbed	I must not have been thumbing
you must not have been thumbing
he must not have been thumbing
we must not have been thumbing
you must not have been thumbing
they must not have been thumbing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I thumb?
must you thumb?
must he thumb?
must we thumb?
must you thumb?
must they thumb? 	must I be thumbing?
must you be thumbing?
must he be thumbing?
must we be thumbing?
must you be thumbing?
must they be thumbing? 	must I have thumbed?
must you have thumbed?
must he 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 he 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 	
must I not thumb?
must you not thumb?
must he not thumb?
must we not thumb?
must you not thumb?
must they not thumb? 	must I not be thumbing?
must you not be thumbing?
must he not be thumbing?
must we not be thumbing?
must you not be thumbing?
must they not be thumbing? 	must I not have thumbed?
must you not have thumbed?
must he not have thumbed?
must we not have thumbed?
must you not have thumbed?
must they not have thumbed? 	must I not have been thumbing?
must you not have been thumbing?
must he not have been thumbing?
must we not have been thumbing?
must you not have been thumbing?
must they not have been thumbing?