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: Did other scientists keep blending inheritance open for further consideration? Passage:In the preface, Fisher considers some general points, including that there must be an understanding of natural selection distinct from that of evolution, and that the then-recent advances in the field of genetics (see history of genetics) now allowed this. In the first chapter, Fisher considers the nature of inheritance, rejecting blending inheritance, because it would eliminate genetic variance, in favour of particulate inheritance. The second chapter introduces Fisher's fundamental theorem of natural selection. The third considers the evolution of dominance, which Fisher believed was strongly influenced by modifiers. Other chapters discuss parental investment, Fisher's geometric model, concerning how spontaneous mutations affect biological fitness, Fisher's principle which explains why the sex ratio between males and females is almost always 1:1, reproductive value, examining the demography of having girl children. Using his knowledge of statistics, the Fisherian runaway, which explores how sexual selection can lead to a positive feedback runaway loop, producing features such as the peacock's plumage. He also wrote about the evolution of dominance, which explores genetic dominance. The last five chapters (8-12) include Fisher's more idiosyncratic views on eugenics.
Links: a. Sexual selection b. Demography c. Blending inheritance d. Parental investment

Ex Output:
c

Ex Input:
Question: How long had the Royal Canadian Air Force existed the year that the McDonnell CF-101 Voodoo began being operated by them? Passage:The McDonnell CF-101 Voodoo was an all-weather interceptor aircraft operated by the Royal Canadian Air Force and the Canadian Forces between 1961 and 1984. They were manufactured by the McDonnell Aircraft Corporation of St. Louis, Missouri for the United States Air Force (as F-101s), and later sold to Canada. CF-101s replaced the obsolete Avro CF-100 Canuck in the RCAF's all-weather fighter squadrons. The Voodoo's primary armament was nuclear AIR-2A Genie unguided air-to-air rockets, and there was significant political controversy in Canada about their adoption. Although they never fired a weapon in wartime, the CF-101 served as Canada's primary means of air defence from Quick Reaction Alert facilities at Canadian airbases. The CF-101s were retired in the 1980s and replaced with McDonnell Douglas CF-18 Hornet fighters. Many examples are preserved in museums and parks in Canada and the United States.
Links: a. AIR-2 Genie b. Royal Canadian Air Force c. McDonnell Douglas CF-18 Hornet d. Royal Canadian Air Force

Ex Output:
b

Ex 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

Ex Output:
b