Final answer:
Christians started to learn more about Muslim advances in science and mathematics after the Crusades
Step-by-step explanation:
The answer to your question is A) Crusades.
The Crusades, which began in 1096 and lasted until 1291, were a series of attempts by Christian armies to retake the Holy Lands from Muslims.
While the primary goal of the Crusades was to regain control of Jerusalem, the Crusaders also encountered Muslim advancements in science and mathematics during their interactions in the Middle East.
In fact, when the Catholic Crusaders returned from the Middle East in the 12th and 13th centuries, they brought back with them knowledge of Muslim technological innovations and academic achievements, including advancements in science and mathematics.