Tragedy means death and sorrow. Somber fits best here because a cheerful tone is not appropriate for tragic events.
Comedy - cheerful tone
This is best because a comedy is meant to be funny and happy. It is cheerful and puts smiles on people's faces.
Both - ironic tone
Irony can be used to create humor or suspense. Shakespeare uses irony throughout his plays to create either one of these elements. We see irony in Romeo and Juliet when the entire audience knows the two lovers will die, but they do not. It is also used to create comedy when the audience knows Viola is dressed as a man when in actuality she is a girl.
