According to the old woman, what brings the most happiness to marriage

The correct answer is: A wife's dominance over her husband.

Explanation:

This tale starts with the old woman who is describing her previous marriages and her five husbands, by sharing her thoughts and experiences from her marriages. She confirms that the most important thing in a marriage for a woman is to learn how to gain dominance and control over her husband.

To reiterate her attitude she tells a story about a knight who raped a young girl. Instead of killing him, the king gives him an opportunity to save his life by figuring out what women most desire. He meets an old woman who is offering him an answer, but, after that, he has to do something for her.

The knight gives a correct answer to the king and the old woman asks the knight to marry her. He agrees, but he's really sad because he finds her old, ugly and repulsive. Then, she offers him to choose between two scenarios: to have an old and ugly wife who will be loyal and virtuous or to have a young and beautiful wife who won't be so loyal to him. The knight says the choice is up to her. He kisses her and she becomes a young and beautiful girl, so they lived happily ever after.

The old woman tells this story to confirm her statement about the wife's dominance over her husband, as, at the end of the story, the knight says that the old woman should take a final decision, which means she gained dominance over him.