English verb conjugation
COULD SKETCH

Regular verb: sketch - sketched - sketched

Affirmation

Simple form	V-ing form
I could sketch you could sketch he could sketch we could sketch you could sketch they could sketch	I could be sketching you could be sketching he could be sketching we could be sketching you could be sketching they could be sketching
Perfect	V-ing perfect
I could have sketched you could have sketched he could have sketched we could have sketched you could have sketched they could have sketched	I could have been sketching you could have been sketching he could have been sketching we could have been sketching you could have been sketching they could have been sketching

Negation

Simple form	V-ing form
I couldn't sketch you couldn't sketch he couldn't sketch we couldn't sketch you couldn't sketch they couldn't sketch	I couldn't be sketching you couldn't be sketching he couldn't be sketching we couldn't be sketching you couldn't be sketching they couldn't be sketching
Perfect	V-ing perfect
I couldn't have sketched you couldn't have sketched he couldn't have sketched we couldn't have sketched you couldn't have sketched they couldn't have sketched	I couldn't have been sketching you couldn't have been sketching he couldn't have been sketching we couldn't have been sketching you couldn't have been sketching they couldn't have been sketching

Interrogative form

Simple form	V-ing form
could I sketch? could you sketch? could he sketch? could we sketch? could you sketch? could they sketch?	could I be sketching? could you be sketching? could he be sketching? could we be sketching? could you be sketching? could they be sketching?
Perfect	V-ing perfect
could I have sketched? could you have sketched? could he have sketched? could we have sketched? could you have sketched? could they have sketched?	could I have been sketching? could you have been sketching? could he have been sketching? could we have been sketching? could you have been sketching? could they have been sketching?

Interro-negative form

Simple form	V-ing form
couldn't I sketch? couldn't you sketch? couldn't he sketch? couldn't we sketch? couldn't you sketch? couldn't they sketch?	couldn't I be sketching? couldn't you be sketching? couldn't he be sketching? couldn't we be sketching? couldn't you be sketching? couldn't they be sketching?
Perfect	V-ing perfect
couldn't I have sketched? couldn't you have sketched? couldn't he have sketched? couldn't we have sketched? couldn't you have sketched? couldn't they have sketched?	couldn't I have been sketching? couldn't you have been sketching? couldn't he have been sketching? couldn't we have been sketching? couldn't you have been sketching? couldn't they have been sketching?