Final answer:
In Act IV of Macbeth, Macduff vows to seek revenge against Macbeth for the slaughter of his family.
Step-by-step explanation:
In Act IV of Macbeth, upon hearing about the slaughter of his family, Macduff vows to A. Seek revenge against Macbeth. After discovering the murder of his wife and children, Macduff is filled with grief and anger and swears to avenge their deaths by seeking revenge against Macbeth, who is responsible for the massacre.