must whiten
Regular verb: whiten - whitened- whitened

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must whiten
you must whiten
she must whiten
we must whiten
you must whiten
they must whiten 	I must be whitening
you must be whitening
she must be whitening
we must be whitening
you must be whitening
they must be whitening	I must have whitened
you must have whitened
she must have whitened
we must have whitened
you must have whitened
they must have whitened	I must have been whitening
you must have been whitening
she must have been whitening
we must have been whitening
you must have been whitening
they must have been whitening	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must not whiten
you must not whiten
she must not whiten
we must not whiten
you must not whiten
they must not whiten 	I must not be whitening
you must not be whitening
she must not be whitening
we must not be whitening
you must not be whitening
they must not be whitening	I must not have whitened
you must not have whitened
she must not have whitened
we must not have whitened
you must not have whitened
they must not have whitened	I must not have been whitening
you must not have been whitening
she must not have been whitening
we must not have been whitening
you must not have been whitening
they must not have been whitening	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I whiten?
must you whiten?
must she whiten?
must we whiten?
must you whiten?
must they whiten? 	must I be whitening?
must you be whitening?
must she be whitening?
must we be whitening?
must you be whitening?
must they be whitening? 	must I have whitened?
must you have whitened?
must she have whitened?
must we have whitened?
must you have whitened?
must they have whitened? 	must I have been whitening?
must you have been whitening?
must she have been whitening?
must we have been whitening?
must you have been whitening?
must they have been whitening? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I not whiten?
must you not whiten?
must she not whiten?
must we not whiten?
must you not whiten?
must they not whiten? 	must I not be whitening?
must you not be whitening?
must she not be whitening?
must we not be whitening?
must you not be whitening?
must they not be whitening? 	must I not have whitened?
must you not have whitened?
must she not have whitened?
must we not have whitened?
must you not have whitened?
must they not have whitened? 	must I not have been whitening?
must you not have been whitening?
must she not have been whitening?
must we not have been whitening?
must you not have been whitening?
must they not have been whitening?