Answer:
Statement A must be sadder than B because of the modal verb 'Must'.
Must expresses strong certainty while Might expresses a possible state in the past or not sure about something in the present or future
These are some of the modals. The modal verbs are used to express ability, possibility, permission or obligation. Each one of the modal verbs can be used to express one or more of these modalities. They can also be used to form the future tense in English and to make conditional sentences.
