I can sketch you can sketch he can sketch we can sketch you can sketch they can sketch
V-ing form
I can be sketching you can be sketching he can be sketching we can be sketching you can be sketching they can be sketching
Perfect
I can have sketched you can have sketched he can have sketched we can have sketched you can have sketched they can have sketched
V-ing perfect
I can have been sketching you can have been sketching he can have been sketching we can have been sketching you can have been sketching they can have been sketching
Negation
Simple form
I can't sketch you can't sketch he can't sketch we can't sketch you can't sketch they can't sketch
V-ing form
I can't be sketching you can't be sketching he can't be sketching we can't be sketching you can't be sketching they can't be sketching
Perfect
I can't have sketched you can't have sketched he can't have sketched we can't have sketched you can't have sketched they can't have sketched
V-ing perfect
I can't have been sketching you can't have been sketching he can't have been sketching we can't have been sketching you can't have been sketching they can't have been sketching
Interrogative form
Simple form
can I sketch? can you sketch? can he sketch? can we sketch? can you sketch? can they sketch?
V-ing form
can I be sketching? can you be sketching? can he be sketching? can we be sketching? can you be sketching? can they be sketching?
Perfect
can I have sketched? can you have sketched? can he have sketched? can we have sketched? can you have sketched? can they have sketched?
V-ing perfect
can I have been sketching? can you have been sketching? can he have been sketching? can we have been sketching? can you have been sketching? can they have been sketching?
Interro-negative form
Simple form
can't I sketch? can't you sketch? can't he sketch? can't we sketch? can't you sketch? can't they sketch?
V-ing form
can't I be sketching? can't you be sketching? can't he be sketching? can't we be sketching? can't you be sketching? can't they be sketching?
Perfect
can't I have sketched? can't you have sketched? can't he have sketched? can't we have sketched? can't you have sketched? can't they have sketched?
V-ing perfect
can't I have been sketching? can't you have been sketching? can't he have been sketching? can't we have been sketching? can't you have been sketching? can't they have been sketching?