The correct option is A. he wanted to avenge the death of his brother. Detailed Explanation:

1. Context of the Story: To understand why Joab murdered Abner, we need to look at the background of the events in the biblical narrative. Joab was the commander of King David's army, and Abner was the commander of Saul's army. The conflict between the houses of Saul and David led to a civil war in Israel.
2. The Death of Joab's Brother: Joab's brother, Asahel, was killed by Abner during a battle. Asahel was pursuing Abner, and in self-defense, Abner struck him down. This incident deeply affected Joab, as it was a personal loss for him. In ancient cultures, avenging the death of a family member was considered a duty and a matter of honor.
3. Joab's Motivation: Joab's motivation for killing Abner was primarily driven by the desire for revenge for his brother's death. This is a common theme in many ancient narratives, where personal honor and family loyalty often lead to cycles of violence. Joab saw Abner not just as a military opponent but as the man responsible for his brother's death, which fueled his desire for vengeance.
4. The Role of David: It is also important to note that David had made peace with Abner and had plans to unite the tribes of Israel under his rule. Joab's actions were not only a personal vendetta but also a political move that undermined David's efforts to consolidate power. Joab acted independently, showing that his loyalty to his brother outweighed his loyalty to David's political agenda.

Why the Other Options Are Incorrect:

• B. he was jealous of Abner: While jealousy can be a motive for conflict, it is not the primary reason for Joab's actions in this case. Joab's actions were rooted in a personal vendetta rather than jealousy over Abner's position or influence. Jealousy would imply that Joab was envious of Abner's power or status, which is not supported by the narrative.
• C. Abner wanted to take his office from him: There is no strong evidence in the biblical text to suggest that Abner was actively trying to usurp Joab's position. While there were political tensions, Joab's murder of Abner was not primarily motivated by a fear of losing his office. Instead, it was about avenging his brother's death.
• D. Abner visited David in Joab's absence: While it is true that Abner's visit to David occurred when Joab was absent, this alone does not justify Joab's murder of Abner. Joab's actions were not a direct response to Abner's visit but rather a culmination of his desire for revenge. The timing of the visit is incidental to the deeper motive of avenging Asahel's death.

Summary:

• Joab murdered Abner primarily to avenge the death of his brother, Asahel.
• The act was driven by personal honor and the cultural expectation of avenging family members.
• Joab's actions undermined David's political efforts, showing a conflict between personal loyalty and political allegiance.
• Other options (jealousy, fear of losing office, and Abner's visit) do not accurately capture Joab's motivations.

This understanding of Joab's actions provides insight into the complexities of loyalty, honor, and the consequences of personal vendettas in biblical narratives.