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: Who was older, Tian Chengsi or Li Baochen? Passage:By 775, one of the military governors who had only nominally been submissive to Emperor Daizong, Tian Chengsi the military governor of Weibo Circuit (魏博, headquartered in modern Handan, Hebei), had particularly offended not only the imperial government but also his fellow warlords—by seizing much of Zhaoyi Circuit (昭義, headquartered in modern Anyang, Henan) after the death of its military governor Xue Song in 773; by looking down on Li Zhengji the military governor of Pinglu Circuit (平盧, headquartered in modern Tai'an, Shandong) and Li Baochen the military governor of Chengde (成德, headquartered in modern Shijiazhuang, Hebei); and by killing Li Baochen's brother Li Baozheng (李寶正), who was also his son-in-law, after his own son Tian Wei (田維) died after colliding with Li Baozhen while playing polo. Li Baochen and Li Zhengji thus offered to attack Tian, and Emperor Daizong decided to take this opportunity to destroy the rebellious Tian. As Zhu Tao was then submissive to the imperial government, he joined forces with Li Baochen and another general loyal to the imperial government, Xue Jianxun (薛兼訓), to attack Weibo from the north, while Li Zhengji and Li Zhongchen attacked from the south. The joint forces had initial successes, but when Zhu and Li Baochen attacked Cang Prefecture (滄州, in modern Cangzhou, Hebei), which was defended by Tian's cousin Tian Tingjie (田庭玠), they could not capture it quickly. Meanwhile, Tian Chengsi had persuaded Li Zhengji to withdraw with flattery. In addition, Li Baochen was offended when an imperial eunuch, Ma Chengqian (馬承倩), who had visited Li Baochen's army, was so dissatisfied with Li Baochen's gift to him that he threw it on the ground, and Tian was also able to use hoaxes to persuade Li Baochen that if he joined forces with Tian to attack Lulong, he would be successful. Li Baochen thus turned against Zhu, launching a surprise attack on him, but was unable to kill Zhu, effectively ending any hopes of the campaign against Tian and subsequently creating an enmity between the Chengde and Lulong Circuits. Emperor Daizong was subsequently forced to reaccept Tian Chengsi's nominal submission.
 Links: a. Tai'an b. Polo c. Shandong d. Li Baochen
Example Output: d

Example Input: Question: How many months/years passed between the signing of the Adams-Onis Treaty and the acquisition of Florida? Passage:Born in Braintree, Massachusetts, Adams spent much of his youth in Europe, where his father served as a diplomat. After returning to the United States, Adams established a successful legal practice in Boston. In 1794, President George Washington appointed Adams as the U.S. ambassador to the Netherlands, and Adams would serve in high-ranking diplomatic posts until 1801, when Thomas Jefferson took office as president. Federalist leaders in Massachusetts arranged for Adams's election to the United States Senate in 1802, but Adams broke with the Federalist Party over foreign policy and was denied re-election. In 1809, Adams was appointed as the U.S. ambassador to Russia by President James Madison, a member of the Democratic-Republican Party. Adams held diplomatic posts for the duration of Madison's presidency, and he served as part of the American delegation that negotiated an end to the War of 1812. In 1817, newly-elected President James Monroe selected Adams as his Secretary of State. In that role, Adams negotiated the Adams–Onís Treaty, which provided for the American acquisition of Florida. He also helped formulate the Monroe Doctrine, which became a key tenet of U.S. foreign policy.
 Links: a. George Washington b. Braintree, Massachusetts c. Adams–Onís Treaty d. Florida
Example Output: c

Example Input: Question: Which Williams sister is the oldest? Passage:In 2014, Ivanovic enjoyed a resurgence and attained a number of career-best achievements. She began the year by winning her first title in three years at the ASB Classic, defeating former world No. 1 Venus Williams in three sets before upsetting the reigning world No. 1 Serena Williams en route to her second Australian Open quarterfinal where she lost in three sets to thirtieth seed, Eugenie Bouchard. During the clay court season, Ivanovic reached her third final of the year at the Porsche Tennis Grand Prix, losing to two-time defending champion Maria Sharapova; the quarterfinals of the Mutua Madrid Open and the semi-finals of the Internazionali BNL d'Italia, defeating Sharapova for the first time since 2007 en route but was ultimately upset by Lucie Šafářová in the third round of the French Open. She rebounded by winning her first career singles title on grass at the Aegon Classic before reaching the final of the Western & Southern Open (her first top tier Premier final since 2009) and thus returned to the top ten of the WTA rankings for the first time in five years as a result. In September, Ivanovic reached her sixth singles final of the year (a new career-best) at the Toray Pan Pacific Open, where she defeated Caroline Wozniacki to claim her fourth title of the season, the most titles she won in a single season.
 Links: a. 2014 WTA Tour b. Eugenie Bouchard c. 2014 Porsche Tennis Grand Prix d. Venus Williams
Example Output:
d