Final answer:
Catherine de Medici arranged a marriage between Henry of Navarre and Margaret of Valois in 1572, option C is the correct answer. This effort for peace was shortly followed by the St. Bartholomew's Day Massacre, profoundly affecting French history and leading to Henry IV's rise to the throne.
Step-by-step explanation:
In 1572, as part of her efforts to make peace between French Catholics and Huguenots, Catherine de Medici arranged a marriage between Henry of Navarre and Margaret of Valois, which makes the correct answer C) Henry III and Margaret of Valois. This marriage was seen as a political maneuver to reconcile the warring religious factions in France. However, it was shortly followed by the St. Bartholomew's Day Massacre, a horrific event where thousands of Huguenots were killed in Paris and throughout France.
Henry of Navarre would later become Henry IV and converted to Catholicism to ascend to the French throne. He eventually issued the Edict of Nantes in 1598, which granted significant rights to the Huguenots, bringing some stability to France after decades of religious conflict.