The correct answer is:
d. He is furious that he has done the work to become king and Banquo's descendants will benefit.
In Shakespeare's "Macbeth," Macbeth is troubled by the witches' prophecy that Banquo's descendants will be kings, which creates a threat to his own power and lineage. Macbeth fears that despite his efforts to gain the throne, it will ultimately pass to Banquo's heirs. This motivates him to want Banquo and his son Fleance dead.