The correct answer is D.
The witches told Macbeth two prophecies: that he would become thane of Cawdor and that, later, he would become the King of Scotland. But they also told Banquo that, even though he would not be King himself, his children would take the crown.
At first, Macbeth doubted the witches, but when he was announced that he had, indeed, been made thane of Cawdor, he believed that the rest of the prophecies would become true as well. This meant that Banquo and his children went from being friends to being a menance for his reign.