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.

Ex 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 Fabrica, during the 199091 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 19992000 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 22 draw against Athletic Bilbao at San Mames Stadium. In May 2000, he became the youngest ever goalkeeper to play in and win a Champions League final when Real Madrid defeated Valencia 30, just four days after his 19th birthday.
Links: a. Olympiacos F.C. b. Real Madrid CF (youth) c. La Fabrica d. Real Madrid CF (youth)

Ex Output:
b

Ex Input:
Question: How old was Yoshinaka when Enichi-ji's general was killed? Passage:Enichi-ji was opened in 807 by the Hosso sect scholar-monk Tokuitsu, who had come from Nara to spread the faith in the Aizu region. He overcame the followers of the Tendai and Shingon sects to become preeminent in Aizu, and by the time of his death in 842, the temples was a complete Shichido garan with 300 monks in residence, several thousand sohei and more than 3500 sub-temples. By the late Heian period, the temple had extended its holdings into eastern Echigo province and had established close ties with the Taira clan. During the Genpei War, the temple sent troops in support of the Heike in Shinano Province against Kiso Yoshinaka. However, the temple's leading general, Jotan-bo, was killed at the 1181 Battle of Yokotagawa by Yoshinaka's forces, and the temple's forces withdrew and the temple went into decline.
Links: a. Heian period b. Shinano Province c. East Asian Yogacara d. Minamoto no Yoshinaka

Ex Output:
d

Ex Input:
Question: How old is the person who sung Glamorous Sky? Passage:"Glamorous Sky" is Mika Nakashima's 16th single overall, her 1st under the name Nana starring Mika Nakashima, and the second most successful single in her career after "Stars". It is her first rock song and it was used as one of the image songs for the film Nana (as one of the bands Black Stones' song). Hyde of L'Arc-en-Ciel composed "Glamorous Sky", while Yazawa Ai wrote the lyrics. The second and third B-sides, "Blood" and "Isolation" were used as CM songs for Kate cosmetics. Mika Nakashima graces the cover of the single as Nana Osaki. The song is featured as a cover by a jrock band, Girugamesh, in the Konami music games, BEMANI for Drummania V3 and Guitarfreaks V3, as well as the iNiS rhythm game Moero! Nekketsu Rhythm Damashii Osu! Tatakae! Ouendan 2.
Links: a. Hyde (musician) b. List of Nana characters c. Mika Nakashima d. Mika Nakashima

Ex Output:
c