must thwack
Regular verb: thwack - thwacked- thwacked

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must thwack
you must thwack
she must thwack
we must thwack
you must thwack
they must thwack 	I must be thwacking
you must be thwacking
she must be thwacking
we must be thwacking
you must be thwacking
they must be thwacking	I must have thwacked
you must have thwacked
she must have thwacked
we must have thwacked
you must have thwacked
they must have thwacked	I must have been thwacking
you must have been thwacking
she must have been thwacking
we must have been thwacking
you must have been thwacking
they must have been thwacking	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't thwack
you mustn't thwack
she mustn't thwack
we mustn't thwack
you mustn't thwack
they mustn't thwack 	I mustn't be thwacking
you mustn't be thwacking
she mustn't be thwacking
we mustn't be thwacking
you mustn't be thwacking
they mustn't be thwacking	I mustn't have thwacked
you mustn't have thwacked
she mustn't have thwacked
we mustn't have thwacked
you mustn't have thwacked
they mustn't have thwacked	I mustn't have been thwacking
you mustn't have been thwacking
she mustn't have been thwacking
we mustn't have been thwacking
you mustn't have been thwacking
they mustn't have been thwacking	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I thwack?
must you thwack?
must she thwack?
must we thwack?
must you thwack?
must they thwack? 	must I be thwacking?
must you be thwacking?
must she be thwacking?
must we be thwacking?
must you be thwacking?
must they be thwacking? 	must I have thwacked?
must you have thwacked?
must she have thwacked?
must we have thwacked?
must you have thwacked?
must they have thwacked? 	must I have been thwacking?
must you have been thwacking?
must she have been thwacking?
must we have been thwacking?
must you have been thwacking?
must they have been thwacking? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I thwack?
mustn't you thwack?
mustn't she thwack?
mustn't we thwack?
mustn't you thwack?
mustn't they thwack? 	mustn't I be thwacking?
mustn't you be thwacking?
mustn't she be thwacking?
mustn't we be thwacking?
mustn't you be thwacking?
mustn't they be thwacking? 	mustn't I have thwacked?
mustn't you have thwacked?
mustn't she have thwacked?
mustn't we have thwacked?
mustn't you have thwacked?
mustn't they have thwacked? 	mustn't I have been thwacking?
mustn't you have been thwacking?
mustn't she have been thwacking?
mustn't we have been thwacking?
mustn't you have been thwacking?
mustn't they have been thwacking?