I can butter you can butter he can butter we can butter you can butter they can butter
V-ing form
I can be buttering you can be buttering he can be buttering we can be buttering you can be buttering they can be buttering
Perfect
I can have buttered you can have buttered he can have buttered we can have buttered you can have buttered they can have buttered
V-ing perfect
I can have been buttering you can have been buttering he can have been buttering we can have been buttering you can have been buttering they can have been buttering
Negation
Simple form
I can't butter you can't butter he can't butter we can't butter you can't butter they can't butter
V-ing form
I can't be buttering you can't be buttering he can't be buttering we can't be buttering you can't be buttering they can't be buttering
Perfect
I can't have buttered you can't have buttered he can't have buttered we can't have buttered you can't have buttered they can't have buttered
V-ing perfect
I can't have been buttering you can't have been buttering he can't have been buttering we can't have been buttering you can't have been buttering they can't have been buttering
Interrogative form
Simple form
can I butter? can you butter? can he butter? can we butter? can you butter? can they butter?
V-ing form
can I be buttering? can you be buttering? can he be buttering? can we be buttering? can you be buttering? can they be buttering?
Perfect
can I have buttered? can you have buttered? can he have buttered? can we have buttered? can you have buttered? can they have buttered?
V-ing perfect
can I have been buttering? can you have been buttering? can he have been buttering? can we have been buttering? can you have been buttering? can they have been buttering?
Interro-negative form
Simple form
can't I butter? can't you butter? can't he butter? can't we butter? can't you butter? can't they butter?
V-ing form
can't I be buttering? can't you be buttering? can't he be buttering? can't we be buttering? can't you be buttering? can't they be buttering?
Perfect
can't I have buttered? can't you have buttered? can't he have buttered? can't we have buttered? can't you have buttered? can't they have buttered?
V-ing perfect
can't I have been buttering? can't you have been buttering? can't he have been buttering? can't we have been buttering? can't you have been buttering? can't they have been buttering?