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 many miles long is the river that Silvanus drove the Alamanni tribesmen back from? Passage:Silvanus was born in Gaul, the son of Bonitus, a Laetic Frankish general who had supported Constantine I in the civil war against Licinius. Like so many other Franks of his times, and like his father before him, he was a loyal and thoroughly romanized "barbarian" in the military service of the Empire. By AD 351, he held the rank of tribune and was one of the senior officers who defected to Emperor Constantius II at the Battle of Mursa Major, after initially supporting the usurper Magnentius. An able soldier, Silvanus was eventually promoted to the rank of Magister militum per Gallias, a crucial post, then in AD 352-353, Constantius personally entrusted him with the difficult task of driving the Alamanni tribesmen raiding and looting in Gaul back beyond the Rhine, and restoring the fast eroding Roman authority in the province. This Silvanus fulfilled partly by bribing the Alamanni chieftains with the taxes he had collected, partly by defeating the Alamanni in battle and partly by suppressing the local bagaudae insurrections flaring up again in central and northern Gaul.
 Links: a. Bonitus (magister militum) b. Constantine the Great c. Rhine d. Rhine
Example Output: c

Example Input: Question: Which group ruled the area for a longer period of time, the Arabs or the Byzantines? Passage:The first permanent Arab settlement on Sicily occurred in 827, but it was not until Taormina fell in 902 that the entire island fell under their sway, though Rometta held out until 965. In that year the Kalbids established the independence of their emirate from the Fatimid Caliphate. In 1061 the first Norman liberators took Messina, and by 1071 Palermo and its citadel (1072) were captured. In 1091 Noto fell to the Normans, and the conquest was complete. Malta fell later that year, though the Arab administration was kept in place, marking the final chapter of this period. The conquests of the Normans established Roman Catholicism firmly in the region, where Eastern Christianity had been prominent during the time of Byzantine rule and even remained significant during Islamic period. Widespread conversion ensued, leading to the disappearance of Islam in Sicily by the 1280s. In 1245, Muslim Sicilians were deported to the settlement of Lucera, by order of Holy Roman Emperor Frederick II. In 1300, Giovanni Pipino da Barletta, count of Altamura, seized Lucera and exiled or sold into slavery its population, bringing an end to the medieval Muslim presence in Italy.
 Links: a. Messina b. Taormina c. Frederick II, Holy Roman Emperor d. Frederick II, Holy Roman Emperor
Example Output: b

Example Input: Question: Which media outlet where Levin's work has appeared has been in business for the longest period of time? Passage:Levin holds several patents in chip design and GPS-based authentication, and has published over 50 scientific papers and policy articles. His work has appeared in Foreign Affairs, Foreign Policy, HuffPost, Politico.com, and the Obama White House website. "How to Counter Fake News," an article Levin co-authored with former Governor of Maryland Martin O'Malley, was included in Foreign Affairs's "The Best of 2017" anthology. He has co-authored pieces on cybersecurity with retired General Wesley Clark, and with cybersecurity expert Dan E. Geer Jr.. He also wrote an article with former Under Secretary of Defense for Policy Michèle Flournoy that encourages the Federal Government to embrace practices that protect data and personal identity from the inside out. He recently collaborated with General H. Hugh Shelton and Stephen Ondra on a report that urges the Department of Defense to choose an open source electronic health record when reforming the Military Health System.
 Links: a. Foreign Policy b. Politico c. Foreign Affairs d. Martin O'Malley
Example Output:
c