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: Where was Thomas Kenan's great grandfather born? Passage:Thomas Stephen Kenan (February 12, 1838 – December 23, 1911) was a Confederate soldier, and later a politician. His parents were Sarah Rebecca Graham and Owen Rand Kenan; he was the grandson of U.S. Congressman Thomas Kenan and great-grandson of Revolutionary War general James Kenan. He started his education in Duplin County, North Carolina at Old Grove Academy in Kenansville (the town was named for his great-grandfather in 1818). Later he spent a year at Central Military Institute in Selma, Alabama. Thomas spent his freshman year of college at Wake Forest in June. Thomas then transferred his sophomore year to the University of North Carolina, where he would graduate in 1857. He studied law for two years with Judge Pearson at Richmond Hill where he practiced law in Kenansville. After graduation and during the Civil War he became Captain of the Duplin Rifles in the Confederate States Army, elected lieutenant colonel of the 43rd North Carolina Infantry Regiment in April 1862, and was promoted to colonel later that year. He was wounded at the Battle of Gettysburg. While on an ambulance train, he and his older brother James Kenan were both captured; they were then imprisoned on Johnson's Island, Ohio. On March 22, 1865, he was released on parole but never switched sides during the war. On his return home he was elected to the state legislature from 1865 to 1867. Later that year he ran for Congress and lost. Not letting that defeat end his political career, he moved to Wilson, North Carolina, where he became mayor and was elected North Carolina Attorney General, serving from 1877 to 1885. In May 1868 he married Miss Sallie Dortch, but they had no children; Sallie died in 1916.
 Links: a. 43rd North Carolina Infantry b. American Civil War c. Owen Rand Kenan d. James Kenan
Example Output: d

Example Input: Question: Who is the current leader of the clan that ruled the Choshu domain? Passage:The area around present-day Atsugi city has been inhabited for thousands of years. Archaeologists have found ceramic shards from the Jōmon period at numerous locations in the area. By the Kamakura period, this area part of the Mōri shōen, part of the holdings of Ōe no Hiromoto. His descendants, the Mōri clan later ruled Chōshū domain. During the Kamakura period, the area was also known for its foundry industry for the production of bells for Buddhist temples. The area came under the control of the Ashikaga clan in the early Muromachi period and was later part of the territories of the Later Hōjō clan from Odawara. With the start of the Edo period, the area was tenryō territory controlled directly by the Tokugawa shogunate, but administered through various hatamoto, as well as exclaves under the control of Odawara Domain, Sakura Domain, Mutsuura Domain, Ogino-Yamanaka Domain and Karasuyama Domain. After the Meiji Restoration, the area was consolidated into Aikō District of Kanagawa Prefecture by 1876. Atsugi town was created on April 1, 1889 through merger of several small hamlets. Atsugi was elevated to city status on February 1, 1955 through merger with neighboring Mutsuai Village, Koaiyu Village, Tamagawa Village and Minamimori Village. The city expanded on July 8, 1958 through merger with neighboring Echi Village, and with Aikawa Village from Naka District. On September 30, 1956, Ogino Village joined with Atsugi. In April 2000, Atsugi exceeded 200,000 in population and was proclaimed a special city with increased autonomy from the central government.
 Links: a. Meiji Restoration b. Mōri clan c. Shōen d. Karasuyama Domain
Example Output: b

Example Input: Question: When was the antibiotic that's used in treatments for syphilitic aortitis discovered? Passage:Syphilitic aortitis is inflammation of the aorta associated with the tertiary stage of syphilis infection. SA begins as inflammation of the outermost layer of the blood vessel, including the blood vessels that supply the aorta itself with blood, the vasa vasorum. As SA worsens, the vasa vasorum undergo hyperplastic thickening of their walls thereby restricting blood flow and causing ischemia of the outer two-thirds of the aortic wall. Starved for oxygen and nutrients, elastic fibers become patchy and smooth muscle cells die. If the disease progresses, syphilitic aortitis leads to an aortic aneurysm. Overall, tertiary syphilis is a rare cause of aortic aneurysms. Syphilitic aortitis has become rare in the developed world with the advent of penicillin treatments after World War II.
  Links: a. Penicillin b. Ischemia c. Aorta d. Aortitis
Example Output:
a