English verb conjugation
MUST BIFF

Regular verb: biff - biffed - biffed

Affirmation

Simple form	V-ing form
I must biff you must biff he must biff we must biff you must biff they must biff	I must be biffing you must be biffing he must be biffing we must be biffing you must be biffing they must be biffing
Perfect	V-ing perfect
I must have biffed you must have biffed he must have biffed we must have biffed you must have biffed they must have biffed	I must have been biffing you must have been biffing he must have been biffing we must have been biffing you must have been biffing they must have been biffing

Negation

Simple form	V-ing form
I must not biff you must not biff he must not biff we must not biff you must not biff they must not biff	I must not be biffing you must not be biffing he must not be biffing we must not be biffing you must not be biffing they must not be biffing
Perfect	V-ing perfect
I must not have biffed you must not have biffed he must not have biffed we must not have biffed you must not have biffed they must not have biffed	I must not have been biffing you must not have been biffing he must not have been biffing we must not have been biffing you must not have been biffing they must not have been biffing

Interrogative form

Simple form	V-ing form
must I biff? must you biff? must he biff? must we biff? must you biff? must they biff?	must I be biffing? must you be biffing? must he be biffing? must we be biffing? must you be biffing? must they be biffing?
Perfect	V-ing perfect
must I have biffed? must you have biffed? must he have biffed? must we have biffed? must you have biffed? must they have biffed?	must I have been biffing? must you have been biffing? must he have been biffing? must we have been biffing? must you have been biffing? must they have been biffing?

Interro-negative form

Simple form	V-ing form
must I not biff? must you not biff? must he not biff? must we not biff? must you not biff? must they not biff?	must I not be biffing? must you not be biffing? must he not be biffing? must we not be biffing? must you not be biffing? must they not be biffing?
Perfect	V-ing perfect
must I not have biffed? must you not have biffed? must he not have biffed? must we not have biffed? must you not have biffed? must they not have biffed?	must I not have been biffing? must you not have been biffing? must he not have been biffing? must we not have been biffing? must you not have been biffing? must they not have been biffing?