Concerning the Future Perfect Continuous, analyze the following items.

I. We use will/shall + have + been + the -ing form of the verb.

II. We use shall only for future time reference with I and we.

III. Shall is more informal and less common than will.

IV. We use the future perfect continuous form when we are looking back to the past from a point in the future and we want to emphasise the length or duration of na activity or event.

Choose the correct answer: