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: How long had Juan Carlos Ongania been leading Argentina by the year La balsa was written? Passage:"La balsa" (; Spanish for "the raft") is the debut single by the Argentine band Los Gatos, released on July 3, 1967 on Vik, a subsidiary of RCA Victor. Formed in 1967 after the disbandment of Los Gatos Salvajes, Los Gatos were the house band of the bar La Cueva, which became a popular meeting place for rock enthusiasts and the birthplace of Argentine rockknown locally as rock nacional (Spanish for "national rock"). During the mid-to-late 1960s, Buenos Aires was experiencing a cultural blossoming characterized by innovations in modern art, literature and cinema, largely driven by a burgeoning youth subculture that adhered to the countercultural phenomenon of the decade. The underground had its center in La Cueva, Plaza Francia and the Torcuato di Tella Institute, and identified with British Invasion music and the sexual revolution. "La balsa" was written by Litto Nebbialead vocalist of the bandand Tanguito (credited as Ramses) on May 2, 1967, in the men's toilet of La Perla de Once, another bar frequented by the group. At the time, Argentina was under a military dictatorship led by Juan Carlos Ongania, which regularly imprisoned and persecuted these young bohemians.
Links: a. British Invasion b. Juan Carlos Ongania c. Argentine rock d. Tanguito
Example Output: b

Example Input: Question: How many people lived in Milan when Diocletian restored political stability after the Crisis of the Third Century? Passage:During the Crisis of the Third Century the Roman Empire nearly collapsed under the combined pressures of invasions, military anarchy and civil wars, and hyperinflation. In 284, emperor Diocletian restored political stability. He carried out thorough administrative reforms to maintain order. He created the so-called Tetrarchy whereby the empire was ruled by two senior emperors called Augusti and two junior vice-emperors called Caesars. He decreased the size of the Roman provinces by doubling their number to reduce the power of the provincial governors. He grouped the provinces into several dioceses (Latin: diocesis) and put them under the supervision of the imperial vicarius (vice, deputy), who was the head of the diocese. During the Crisis of the Third Century the importance of Rome declined because the city was far from the troubled frontiers. Diocletian and his colleagues usually resided in four imperial seats. The Augusti, Diocletian and Maximian, who were responsible for the East and West respectively, established themselves at Nicomedia, in north-western Anatolia (closer to the Persian frontier in the east) and Milan, in northern Italy (closer to the European frontiers) respectively. The seats of the Caesars were Augusta Treverorum (on the River Rhine frontier) for Constantius Chlorus and Sirmium (on the River Danube frontier) for Galerius who also resided at Thessaloniki.
Links: a. Milan b. Danube c. Sirmium d. History of Trier
Example Output: a

Example Input: Question: In which state did the siege of Vicksburg take place? Passage:At the beginning of the Civil War, he became a lieutenant and adjutant of the 13th Iowa Infantry Regiment. He fought at the battle of Shiloh and Corinth. He served as assistant adjutant general in the XVII Corps during the siege of Vicksburg and assistant adjutant general to the Army of the Tennessee during the Atlanta Campaign. He was made a brevet brigadier general for service in the Atlanta Campaign and was assigned to an infantry brigade in the XV Corps during the Carolinas Campaign, but was only lightly engaged in fighting. He rose to the full rank of brigadier general of volunteers (1865), and was made a brevet major general at the close of the same year for gallant and meritorious services during the war.
Links: a. Siege of Vicksburg b. Lieutenant c. Battle of Shiloh d. Siege of Vicksburg
Example Output:
a