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 mustn't biff you mustn't biff he mustn't biff we mustn't biff you mustn't biff they mustn't biff	I mustn't be biffing you mustn't be biffing he mustn't be biffing we mustn't be biffing you mustn't be biffing they mustn't be biffing
Perfect	V-ing perfect
I mustn't have biffed you mustn't have biffed he mustn't have biffed we mustn't have biffed you mustn't have biffed they mustn't have biffed	I mustn't have been biffing you mustn't have been biffing he mustn't have been biffing we mustn't have been biffing you mustn't have been biffing they mustn't 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
mustn't I biff? mustn't you biff? mustn't he biff? mustn't we biff? mustn't you biff? mustn't they biff?	mustn't I be biffing? mustn't you be biffing? mustn't he be biffing? mustn't we be biffing? mustn't you be biffing? mustn't they be biffing?
Perfect	V-ing perfect
mustn't I have biffed? mustn't you have biffed? mustn't he have biffed? mustn't we have biffed? mustn't you have biffed? mustn't they have biffed?	mustn't I have been biffing? mustn't you have been biffing? mustn't he have been biffing? mustn't we have been biffing? mustn't you have been biffing? mustn't they have been biffing?