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.

Example Input: Question: What age bracket plays for the Real Madrid's youth system? Passage:Casillas began his career in Real Madrid's youth system, known as La Fábrica, during the 1990–91 season. On 27 November 1997, at age 16 and still a junior, he was first called up to the senior team squad to face Rosenborg in the UEFA Champions League, although he remained on the bench throughout. After spending a season with the C-team in the fourth tier, during which they won their regional group, he came into contention as the club's first-choice between the posts. In starting the 1999–2000 UEFA Champions League group stage fixture against Olympiakos on 15 September 1999, he became the youngest goalkeeper ever to feature in the competition at the time, aged 18 years and 177 days; a record which was only broken in October 2017 by Mile Svilar. Three days earlier, Casillas had made his La Liga debut in a 2–2 draw against Athletic Bilbao at San Mamés Stadium. In May 2000, he became the youngest ever goalkeeper to play in and win a Champions League final when Real Madrid defeated Valencia 3–0, just four days after his 19th birthday.
 Links: a. Olympiacos F.C. b. Real Madrid CF (youth) c. La Fábrica d. Real Madrid CF (youth)
Example Output: b

Example Input: Question: How many years apart were Manuchar and his older brother? Passage:Manuchar I Jaqeli () (1452 – died after 1518) was a Prince and Atabeg of Samtskhe-Saatabago from 1515 to 1518. He was a member of the Jaqeli family and youngest son of Qvarqvare II Jaqeli. After his older brother Mzetchabuk's abdication Manuchar started an uprising against his nephew Qvarqvare, the son of Kaikhosro I. Manuchar's revolt finished successfully and he ascended to the Meskhetian throne. During his brief reign Manuchar sent many gifts to the Ottoman sultan Selim I and claimed himself as an admier of Ottomans. In 1518 the new revolt started. Prince Qvarqvare with the help of Safavid troops attacked Samtskhe. Manuchar was overthrown and Qvarqvare became the new ruler of Meskheti. After this Manuchar asked his suzerain Sultan Selim for help. Sultan gave him the huge army. He had tried to restore himself as Atabeg, but was defeated by Qvarqvare's forces at the battle near Erzurum. Manuchar Jaqeli escaped to the Ottoman empire and lived there until his death. Nothing is known about his later life and descendants.
 Links: a. Selim I b. Mzetchabuk Jaqeli c. Mzetchabuk Jaqeli d. Qvarqvare III Jaqeli
Example Output: b

Example Input: Question: How long had Ferdinand I been in power the year Coimbra fell? Passage:The history of the county of Portugal is traditionally dated from the reconquest of Portus Cale (Porto) by Vímara Peres in 868. He was named a count and given control of the frontier region between the Limia and Douro rivers by Alfonso III of Asturias. South of the Douro, another border county would be formed decades later when what would become the County of Coimbra was conquered from the Moors by Hermenegildo Guterres. This moved the frontier away from the southern bounds of the county of Portugal, but it was still subject to repeated campaigns from the Caliphate of Córdoba. The recapture of Coimbra by Almanzor in 987 again placed the County of Portugal on the southern frontier of the Leonese state for most of the rest of the first county's existence. The regions to its south were only again conquered in the reign of Ferdinand I of León and Castile, with Lamego falling in 1057, Viseu in 1058 and finally Coimbra in 1064.
 Links: a. Reconquista b. Ferdinand I of León c. County of Coimbra d. Hermenegildo Gutiérrez
Example Output:
b