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 years after Wish You Were Here was released was The Wall released? Passage:Storm Thorgerson, who had done the majority of album covers for Pink Floyd, did the Echoes art which features recursive windows in an infinite regression as a nod to his own cover for 1969's Ummagumma, and the objects on each landscape refer to the Pink Floyd discography. For instance, there's the man on fire from Wish You Were Here, another wearing the Delicate Sound of Thunder lightbulb suit, dolls of the Atom Heart Mother cow and the Animals pig, a bike and both a brick wall and the hammers from The Wall. Eventually Thorgerson opted to make two images, with another used for the back cover. To create the idea on a photograph, various walls - which had varied measurements and angles to ensure that "nothing seemed to fit other than by eye through the lens." - were built and put in a country landscape in Sussex. Actors, props and fittings were set in and between those walls. The original design was one of two sketches submitted for Dream Theater's 1997 album Falling into Infinity, with the original being framed and hanging in the home of former Dream Theater drummer Mike Portnoy and is pointed out by Portnoy in his Hudson Music instructional drum DVD In Constant Motion.
 Links: a. Wish You Were Here (Pink Floyd album) b. Sussex c. Ummagumma d. Atom Heart Mother
Example Output: a

Example Input: Question: When was the founding of the city that the crusaders captured? Passage:The See of Tyre was the most prestigious archbishopric under the authority of the patriarchs of Antioch from the 5th century. The archbishops had more than a dozen suffragans, including the bishops of Acre, Beirut, Jubail, Sidon, Tripoli and Tortosa. The crusaders captured Tortosa (now Tartus in Syria) in 1102, Jubail in 1103, and Tripoli in 1109. In the late 1170s, William of Tyre wrote that Bernard of Valence, the Latin Patriarch of Antioch, had soon appointed Latin bishops to the three bishoprics. Documents written in the early 12th century did not refer to the bishops of the three dioceses, suggesting that the three sees, all located in the newly established crusader County of Tripoli, were actually left vacant. After King Baldwin I of Jerusalem captured Sidon and Beirut in 1110, Ghibbelin of Arles, the Latin Patriarch of Jerusalem, convinced Baldwin I to ask Pope Paschal II to place the two sees and also the bishopric of Acre under the jurisdiction of the patriarchs of Jerusalem. Accepting the king's argumentation, the Pope ruled on 8 June 1111 that the boundaries of the ecclesiastical provinces should follow the political frontiers. Patriarch Bernard protested, but the Pope confirmed his decision, emphasizing his right to alter the boundaries of the patriarchates.
 Links: a. Patriarch of Antioch b. Baldwin I of Jerusalem c. Tartus d. William of Tyre
Example Output: c

Example Input: Question: How many years has Serco been operating the NorthLink Ferries? Passage:Serco operates the Santander Cycles scheme (for Transport for London) and the NorthLink Ferries Northern Isles lifeline ferry service in Scotland. Serco also has a joint venture with Abellio, the international arm of Dutch national rail operator Nederlandse Spoorwegen, to operate passenger trains in the UK. Serco-Abellio has a 25-year concession for Merseyrail in Liverpool until 2028 and operated the Northern Rail franchise from December 2004 until March 2016. Serco's Home Affairs division, run by Tom Riall, also operates speed camera systems throughout the UK and, until November 2013, designed, wrote and tested the software that controls the matrix message signs, signals, emergency roadside telephones (SOS) and traffic monitoring on England's motorway network including, until 2011, the National Traffic Control Centre. It previously operated the Docklands Light Railway.
 Links: a. Northern Rail (Serco-Abellio) b. NorthLink Ferries c. Docklands Light Railway d. Liverpool
Example Output:
b