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.

Input: Consider Input: Question: How many years were there between the end of the British Burma Campaign and the start of the Battle of Na San? Passage:The First Indochina War had raged, as guerrilla warfare, since 19 December 1946. From 1949, it evolved into conventional warfare, due largely to aid from the communists of the People's Republic of China ("PRC") to the north. Subsequently, the French strategy of occupying small, poorly defended outposts throughout Indochina, particularly along the Vietnamese-Chinese border, started failing. Thanks to the terrain, popular support for August Revolution and support for decolonization from bordering China and the U.S.S.R., the Viet Minh had succeeded in turning a "clandestine guerrilla movement into a powerful conventional army", following asymmetric warfare theory laid by Mao Tse Tung, something which previously had never been encountered by the western colonial powers. In October 1952, fighting around the Red River Delta spread into the Thai Highlands, resulting in the Battle of Nà Sản, at which the Viet Minh were defeated. The French used the lessons learned at Nà Sản – strong ground bases, versatile air support, and a model based on the British Burma Campaign – as the basis for their new strategy. The Viet Minh, however, remained unbeatable in the highland regions of Vietnam, and the French "could not offset the fundamental disadvantages of a roadbound army facing a hill and forest army in a country which had few roads but a great many hills and forests".
 Links: a. China b. On Guerrilla Warfare c. Battle of Nà Sản d. China

Output: c


Input: Consider Input: Question: How old was the king when he awarded Mairi and Knocker the Order of Léopold II, Knights Cross? Passage:Chisholm and Knocker soon came to the conclusion that they could save more lives by treating the wounded directly on the front lines. In November, they decided to leave the corps and set up their own dressing station five miles east in a town named Pervyse, north of Ypres, just one hundred yards from the trenches. Here, in a vacant cellar which they named "Poste de Secours Anglais" ("British First Aid Post"), the two would spend the next three and a half years tending to the wounded. No longer affiliated with the Belgian Red Cross, they began acting completely as free agents and had to support their work by raising their own funds. Through sheer perseverance Knocker was able to arrange for the two of them to be officially seconded to the Belgian garrison stationed there. In January 1915, they were both decorated by King Albert I of Belgium with the Order of Léopold II, Knights Cross (with palm) for their courageous work on the front lines. They were also awarded the British Military Medal and both made Officers of the Most Venerable Order of St. John of Jerusalem. Chisholm was also decorated with the Queen Elisabeth Medal of Belgium and the British campaign medals, including the 1914 Star. The two became instant celebrities earning the distinction of being among the most photographed women of the war.
 Links: a. Ypres b. Albert I of Belgium c. Queen Elisabeth Medal d. Pervijze

Output: b


Input: Consider Input: Question: Which of the European kings who support the Charlemagne Prize is the oldest? Passage:The Charlemagne Prize (; full name originally Internationaler Karlspreis der Stadt Aachen, International Charlemagne Prize of the City of Aachen, since 1988 Internationaler Karlspreis zu Aachen, International Charlemagne Prize of Aachen) is a prize awarded for work done in the service of European unification. It has been awarded annually since 1950 by the German city of Aachen. It commemorates Charlemagne, ruler of the Frankish Empire and founder of what became the Holy Roman Empire, who resided and is buried in Aachen. Traditionally the award is given to the recipient on Ascension Day in a ceremony in the town hall of Aachen. In April 2008, the organisers of the Charlemagne Prize and the European Parliament jointly created a new European Charlemagne Youth Prize, which recognises contributions by young people towards the process of European integration. Patrons of the foundation are King Philippe of Belgium, King Felipe VI of Spain, and Henri, the Grand Duke of Luxembourg.
 Links: a. Philippe of Belgium b. Francia c. Patronage d. Philippe of Belgium


Output: a