Concept: The Islamic allowance of polygamy is a moral safeguard, not a licence for unlimited marriage or mere social pleasure.Explanation: Islam permits a man to marry up to four wives so that he can live in a lawful relationship instead of committing unlawful sexual acts or adultery.The Qur’an makes this permission conditional: a man must be able to deal justly with all his wives.If he fears that he cannot be fair to them, then he is advised to marry only one wife.Therefore, the protection of chastity is the central aim, while equal treatment is the required condition for the permission.Answer: D. preventing adultery.