English verb conjugation
COULD THUMB

Regular verb: thumb - thumbed - thumbed

Affirmation

Simple form	V-ing form
I could thumb you could thumb he could thumb we could thumb you could thumb they could thumb	I could be thumbing you could be thumbing he could be thumbing we could be thumbing you could be thumbing they could be thumbing
Perfect	V-ing perfect
I could have thumbed you could have thumbed he could have thumbed we could have thumbed you could have thumbed they could have thumbed	I could have been thumbing you could have been thumbing he could have been thumbing we could have been thumbing you could have been thumbing they could have been thumbing

Negation

Simple form	V-ing form
I couldn't thumb you couldn't thumb he couldn't thumb we couldn't thumb you couldn't thumb they couldn't thumb	I couldn't be thumbing you couldn't be thumbing he couldn't be thumbing we couldn't be thumbing you couldn't be thumbing they couldn't be thumbing
Perfect	V-ing perfect
I couldn't have thumbed you couldn't have thumbed he couldn't have thumbed we couldn't have thumbed you couldn't have thumbed they couldn't have thumbed	I couldn't have been thumbing you couldn't have been thumbing he couldn't have been thumbing we couldn't have been thumbing you couldn't have been thumbing they couldn't have been thumbing

Interrogative form

Simple form	V-ing form
could I thumb? could you thumb? could he thumb? could we thumb? could you thumb? could they thumb?	could I be thumbing? could you be thumbing? could he be thumbing? could we be thumbing? could you be thumbing? could they be thumbing?
Perfect	V-ing perfect
could I have thumbed? could you have thumbed? could he have thumbed? could we have thumbed? could you have thumbed? could they have thumbed?	could I have been thumbing? could you have been thumbing? could he have been thumbing? could we have been thumbing? could you have been thumbing? could they have been thumbing?

Interro-negative form

Simple form	V-ing form
couldn't I thumb? couldn't you thumb? couldn't he thumb? couldn't we thumb? couldn't you thumb? couldn't they thumb?	couldn't I be thumbing? couldn't you be thumbing? couldn't he be thumbing? couldn't we be thumbing? couldn't you be thumbing? couldn't they be thumbing?
Perfect	V-ing perfect
couldn't I have thumbed? couldn't you have thumbed? couldn't he have thumbed? couldn't we have thumbed? couldn't you have thumbed? couldn't they have thumbed?	couldn't I have been thumbing? couldn't you have been thumbing? couldn't he have been thumbing? couldn't we have been thumbing? couldn't you have been thumbing? couldn't they have been thumbing?