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 cannot butter you cannot butter he cannot butter we cannot butter you cannot butter they cannot butter
V-ing form
I cannot be buttering you cannot be buttering he cannot be buttering we cannot be buttering you cannot be buttering they cannot be buttering
Perfect
I cannot have buttered you cannot have buttered he cannot have buttered we cannot have buttered you cannot have buttered they cannot have buttered
V-ing perfect
I cannot have been buttering you cannot have been buttering he cannot have been buttering we cannot have been buttering you cannot have been buttering they cannot 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 I not butter? can you not butter? can he not butter? can we not butter? can you not butter? can they not butter?
V-ing form
can I not be buttering? can you not be buttering? can he not be buttering? can we not be buttering? can you not be buttering? can they not be buttering?
Perfect
can I not have buttered? can you not have buttered? can he not have buttered? can we not have buttered? can you not have buttered? can they not have buttered?
V-ing perfect
can I not have been buttering? can you not have been buttering? can he not have been buttering? can we not have been buttering? can you not have been buttering? can they not have been buttering?