Answer:
"D) the king of Scotland"
Explanation:
The predictions which were made by the three witches in the act 1 of "Macbeth" interests Macbeth. But the most interesting prophecy to Macbeth was that one day he will become the "king of Scotland". This is so because the time the witches made the prophecy the present king of Scotland who was Duncan was already alive. Which made Macbeth think, how can he become the "king of Scotland". This prophecy motivated the over ambitious nature inside Macbeth to ignite and act accordingly.