He may leave on Wednesday.
He may not leave on Wednesday.
We should tell her about it.
We shouldn't tell her about it.
We must wait here.
We mustn't wait here.
I can understand him easily.
I can't understand him easily.
You may sit here.
You may not sit here.
We can meet you later.
We can't meet you later.
They can go by plane.
They can't go by plane.
She should sit near the window.
She shouldn't sit near the window.
We must do the same thing again.
We mustn't do the same thing again.
She can play the piano well.
She can't play the piano well.