Final answer:
The 'new alliance' was a marriage between the Protestant king of Navarre, Henry IV, and the Catholic princess Margaret of Valois. This led to religious peace with the Edict of Nantes granting liberties to Huguenots.
Step-by-step explanation:
The "new alliance" made by the king of Navarre referred to in the passage is (A) A marriage between the Protestant king and a Catholic princess. This alliance took place through the marriage of Margaret of Valois to Henry of Navarre, which was shortly followed by the tragic St. Bartholomew's Day Massacre. After many struggles, including the War of the Three Henrys and the deaths of his rivals, Henry of Navarre ascended to the throne as Henry IV. Notably, he converted to Catholicism and issued the Edict of Nantes in 1598, granting liberty of conscience and worship to French Protestants, known as Huguenots, thereby establishing a tentative peace in a deeply divided country.