a. the witches show Macbeth a procession of Banquo's descendants as kings.
Explanation: The event from Act IV of "The Tragedy of Macbeth" by William Shakespeare, that foreshadows Macbeth's eventual downfall is <em>the witches show Macbeth a procession of Banquo's descendants as kings</em>. Foreshadowing is a literary device in which an author gives hints about what is going to happen later. All of the withches' prophecies have come true. The reader is expecting this new vision of Banquo's descendants as kings to be also true.
