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: Which of the regiments that Ellwood served in was the largest? Passage:Ellwood graduated from Duntroon in 1990 and was commissioned into the Royal Australian Infantry Corps. His early career included postings as a platoon commander in the 2nd/4th Battalion, Royal Australian Regiment and as an instructor in field training and tactics at Duntroon, before he was seconded to the British Army from 1998 for a two-year exchange with the Irish Guards, then stationed in Germany. During the secondment he deployed as part of the NATO intervention in the Kosovo War in 1999, serving as second-in-command of an armoured infantry company in the King's Royal Hussars Battle Group. For his service in Kosovo, Ellwood was awarded a Commander British Forces Commendation. He returned to Australia as a company commander and operations officer in the 5th/7th Battalion, Royal Australian Regiment (5/7RAR). Ellwood commanded B Company on operations in East Timor from October 1999 to April 2000, when 5/7RAR deployed with the International Force East Timor.
Links: a. 2nd/4th Battalion, Royal Australian Regiment b. Kosovo War c. 2nd/4th Battalion, Royal Australian Regiment d. King's Royal Hussars
Example Output: a

Example Input: Question: Which road is longer, KY 1319 (Kings Church Road) or KY 155 (Taylorsville Lake Road)? Passage:Kentucky Route 1531 is a rural secondary highway that begins in northeastern Bullitt County and ends in northwestern Shelby County, but the route spends almost all of its length in the city of Louisville in eastern Jefferson County. The highway begins at KY 1319 (Kings Church Road) near Whitfield. KY 1531 heads northwest along Dawson Hill Road then turns northeast onto Routt Road to enter the city of Louisville and Jefferson County. The highway crosses Wheelers Run and Back Run and meets the eastern end of KY 1819 (Brush Run Road) south of the Routt neighborhood of Louisville. KY 1531 follows Sheckels Run to its crossing of Cane Run and reaches KY 155 (Taylorsville Lake Road) south of Fisherville. The highway runs concurrently with KY 155 northwest across Floyds Fork of the Salt River to KY 148 (Taylorsville Road), with which the route heads east through Fisherville and across Floyds Fork again.
Links: a. Kentucky Route 155 b. Louisville, Kentucky c. Fisherville, Louisville d. Concurrency (road)
Example Output: a

Example Input: Question: What year was Robert Kean's son first elected governor? Passage:Kean was born September 28, 1893, in Elberon, New Jersey. His father, Hamilton Fish Kean (18621941), was a United States Senator from New Jersey and his son, Thomas Kean, served two terms as the Governor of New Jersey. Robert Kean was the great-great-grandson of John Kean, a Delegate to the Continental Congress from South Carolina (17561795). His uncle, John Kean (18521914), was also a United States Senator from New Jersey. His grandson, Thomas Kean, Jr., is presently the Minority Leader of the New Jersey State Senate. His mother, Katherine Taylor Winthrop (18661943), was a descendant of John Winthrop, a wealthy English Puritan lawyer and one of the leading figures in the founding of the Massachusetts Bay Colony, the first major settlement in what is now New England after Plymouth Colony. Winthrop led the first large wave of migrants from England in 1630 and served as governor for 12 of the colony's first 20 years of existence. Kean is also a descendant of William Livingston, the first Governor of New Jersey.
Links: a. New Jersey Senate b. William Livingston c. William Livingston d. Thomas Kean
Example Output:
d