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: How long did the Siege of Boston last? Passage:The Battle of Lexington and Concord was the first conflict in the American Revolutionary War. On April 19, 1775, a force of British Army regulars marched from Boston to Concord to capture a cache of arms that was reportedly stored in the town. Forewarned by Samuel Prescott (who had received the news from Paul Revere), the colonists mustered in opposition. Following an early-morning skirmish at Lexington, where the first shots of the battle were fired, the British expedition under the command of Lt. Col. Francis Smith advanced to Concord. There, colonists from Concord and surrounding towns (notably a highly drilled company from Acton led by Isaac Davis) repulsed a British detachment at the Old North Bridge and forced the British troops to retreat. Subsequently, militia arriving from across the region harried the British troops on their return to Boston, culminating in the Siege of Boston and the outbreak of the war.
 Links: a. Old North Bridge b. Paul Revere c. Siege of Boston d. Isaac Davis (soldier)

Ex Output:
c


Ex Input:
Question: Which aircraft had a longer operational lifespan in the Royal Canadian Air Force between the McDonnell CF-101 Voodoo and the Avro CF-100 Canuck? 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. Avro Canada CF-100 Canuck b. Interceptor aircraft c. Interceptor aircraft d. Royal Canadian Air Force

Ex Output:
a


Ex Input:
Question: What was the total number of Junker Ju 88 planes ever built? Passage:By August 1940 the Battle of Britain was intensifying. Most of the battles thus far were in daylight, leaving night-fighter crews frustrated. Now based at RAF Digby in Lincolnshire and operating from the satellite airfield at Wellingore the unit formed part of No. 12 Group RAF defending British air space north of London. On the night of 24 August 1940 Braham took off and patrolled the Humberside area. The Blenheim was piloted by Braham, and contained air gunner Sergeant Wilsdon and aircraftman and trained radar operator N. Jacobson. Braham was directed to an aircraft held in searchlights but he closed too fast and overshot. His gunner succeeded in damaging the aircraft sufficiently and a searchlight crew saw it crash into the sea. It was identified as a Heinkel He 111. Braham's only other interaction with the enemy occurred at Ternhill, when a Junkers Ju 88 dropped bombs on the airfield destroying 13 Avro Ansons and damaged 20 more. Braham survived the attack uninjured.
 Links: a. Junkers Ju 88 b. Junkers Ju 88 c. No. 12 Group RAF d. Junkers Ju 88

Ex Output:

a