You will be given a definition of a task first, then some input of the task.
In this task, you're given a question, a context passage, and four options which are terms from the passage. After reading a passage, you will get a brief understanding of the terms. Your job is to determine by searching and reading further information of which term you can answer the question. Indicate your choice as 'a', 'b', 'c', or 'd'. If you think more than one option is plausible, choose the more probable option to help you answer the question.

Question: How much time had passed between the start of Thirteen Years' War and the purchase of Malbork Castle by King Casimir IV? Passage:It was originally constructed by the Teutonic Knights, a German Catholic religious order of crusaders, in a form of an Ordensburg fortress. The Order named it Marienburg in honour of Mary, mother of Jesus. In 1457, during the Thirteen Years' War, it was sold by the Bohemian mercenaries to King Casimir IV of Poland in lieu of indemnities and it since served as one of the several Polish royal residences and the seat of Polish offices and institutions, interrupted by several years of Swedish occupation, and fulfilling this function until the First Partition of Poland in 1772. From then on the castle was under German rule for over 170 years. Following Germany's defeat in World War II in 1945, the land was assigned to Poland by the Allies. Heavily damaged, the castle was renovated under the auspices of modern-day Poland in the second half of the 20th century and most recently in 2016. Nowadays, the castle hosts exhibitions and serves as a museum.
Links: a. Ordensburg b. Thirteen Years' War (14541466) c. Bohemia d. Mary, mother of Jesus
Output:
b