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: What is the age difference between the father and son who may have built Hauenstejn castle? Passage:The castle was built in the 13th century by Premysl Otakar II or his son Vaclav II to guard royal paths and local mines. The first known owner was Mikulas Winkler, burgrave of Loket Castle, who sold Hauenstejn to the monastery in Doksany. The monastery exchanged it for another building with King John of Luxemburg. His son Charles IV enlarged the castle's domain. The castle frequently changed its keepers in the second half of the 14th century and the 15th century but it more or less remained royal property. The rich family of Slik that started silver mining near Jachymov won the castle in the 16th century. The Sliks rebuilt the castle in the Renaissance style after a fire in 1600. In 1663 the Sliks sold the castle to the Saxe-Lauenburg ducal family and it became part of the Ostrov domain. The castle was in the hands of the Baden family from 1689. When the last male member of the family died in 1771, the property of the Badens in Bohemia was inherited by the royal family of Maria Theresa. The Habsburgs sold it to the Buquoy family in 1837. Countess Gabrielle Buquoy started to rebuild the castle in a Romantic style. Ferdinand Buquoy continued the reconstruction under the influence of historism, taking its examples from England (Windsor, Arundel, Belvoir, Lancaster or Oxford) and Bavaria (Hohenswangau, Lahneck).
Links: a. Ostrov (Karlovy Vary District) b. Historism c. Ottokar II of Bohemia d. Charles IV, Holy Roman Emperor
Output:
c