Final answer:
Louis IX was known for his commitment to social justice, which is reflected in his regular invitations to the poor to dine with him, thus the answer is C) Social justice.
Step-by-step explanation:
Louis IX was well known for his works of social justice and regularly invited people who were poor to eat with him. The correct answer to the student's question is C) Social justice. Louis IX's commitment to the poor and his acts of charity contribute to this association, and his sainthood by the Catholic Church further cements his reputation in this regard. While European royalty often used art, architecture, and education to promote their rule and religious beliefs, Louis IX is particularly remembered for his actions supporting the less fortunate and promoting social harmony within Christian tenets.