English verb conjugation
COULD BIFF

Regular verb: biff - biffed - biffed

Affirmation

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

Negation

Simple form	V-ing form
I couldn't biff you couldn't biff she couldn't biff we couldn't biff you couldn't biff they couldn't biff	I couldn't be biffing you couldn't be biffing she couldn't be biffing we couldn't be biffing you couldn't be biffing they couldn't be biffing
Perfect	V-ing perfect
I couldn't have biffed you couldn't have biffed she couldn't have biffed we couldn't have biffed you couldn't have biffed they couldn't have biffed	I couldn't have been biffing you couldn't have been biffing she couldn't have been biffing we couldn't have been biffing you couldn't have been biffing they couldn't have been biffing

Interrogative form

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

Interro-negative form

Simple form	V-ing form
couldn't I biff? couldn't you biff? couldn't she biff? couldn't we biff? couldn't you biff? couldn't they biff?	couldn't I be biffing? couldn't you be biffing? couldn't she be biffing? couldn't we be biffing? couldn't you be biffing? couldn't they be biffing?
Perfect	V-ing perfect
couldn't I have biffed? couldn't you have biffed? couldn't she have biffed? couldn't we have biffed? couldn't you have biffed? couldn't they have biffed?	couldn't I have been biffing? couldn't you have been biffing? couldn't she have been biffing? couldn't we have been biffing? couldn't you have been biffing? couldn't they have been biffing?