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 people died in the incident that contaminated about 30,000 km?  Passage:Natural strontium is a mixture of four stable isotopes: Sr, Sr, Sr, and Sr. Their abundance increases with increasing mass number and the heaviest, Sr, makes up about 82.6% of all natural strontium, though the abundance varies due to the production of radiogenic Sr as the daughter of long-lived beta-decaying Rb. Of the unstable isotopes, the primary decay mode of the isotopes lighter than Sr is electron capture or positron emission to isotopes of rubidium, and that of the isotopes heavier than Sr is electron emission to isotopes of yttrium. Of special note are Sr and Sr. The former has a half-life of 50.6 days and is used to treat bone cancer due to strontium's chemical similarity and hence ability to replace calcium. While Sr (half-life 28.90 years) has been used similarly, it is also an isotope of concern in fallout from nuclear weapons and nuclear accidents due to its production as a fission product. Its presence in bones can cause bone cancer, cancer of nearby tissues, and leukemia. The 1986 Chernobyl nuclear accident contaminated about 30,000 km with greater than 10 kBq/m with Sr, which accounts for 5% of the core inventory of Sr.
 Links: a. Rubidium b. Mass number c. Electron capture d. Chernobyl disaster

Output: d


Input: Consider Input: Question: Who was older when Heitler obtained his doctorate, Arnold Sommerfeld or Karl Herzfeld? Passage:In 1922, Heitler began his study of physics at the Karlsruhe Technische Hochschule, in 1923 at the Humboldt University of Berlin, and in 1924 at the Ludwig Maximilian University of Munich (LMU), where he studied under both Arnold Sommerfeld and Karl Herzfeld. The latter was his thesis advisor when he obtained his doctorate in 1926; Herzfeld taught courses in theoretical physics and one in physical chemistry, and in Sommerfeld's absence often took over his classes. From 1926 to 1927, he was a Rockefeller Foundation Fellow for postgraduate research with Niels Bohr at the Institute for Theoretical Physics at the University of Copenhagen and with Erwin Schrödinger at the University of Zurich. He then became an assistant to Max Born at the Institute for Theoretical Physics at the University of Göttingen. Heitler completed his Habilitation, under Born, in 1929, and then remained as a Privatdozent until 1933. In that year, he was let go by the university because he was Jewish.
 Links: a. University of Göttingen b. Ludwig Maximilian University of Munich c. Arnold Sommerfeld d. Arnold Sommerfeld

Output: c


Input: Consider Input: Question: Which of the set of islands the expedition visited has a lower latitude? Passage:He led the 1901-1904 Swedish Antarctic Expedition, aboard the ship Antarctic. The expedition visited the Falkland Islands before the ship, commanded by seasoned Antarctic sailor Carl Anton Larsen, dropped Nordenskjöld's party off at Snow Hill Island, a small island off the coast of the Antarctic Peninsula. Nordenskiöld overwintered at Snow Hill Island, while Antarctic returned to the Falklands. The following summer Larsen brought her south, intending to retrieve the Nordenskiöld party, but she became trapped in ice which eventually crushed her hull, forcing Larsen and his crew to overwinter in a hastily constructed shelter on Paulet Island. Larsen and Nordenskjöld finally rendezvoused at their fall-back rescue hut at Hope Bay in late 1903, where they were picked up by the Argentine Navy corvette ARA Uruguay (commanded by Julián Irízar), which had been dispatched when Antarctic had failed to make her appointed return to South America the previous year. Despite its end and the great hardships endured, the expedition was considered a scientific success, with the parties having explored much of the eastern coast of Graham Land, including Cape Longing, James Ross Island, the Joinville Island group, and the Palmer Archipelago. The expedition, which also recovered valuable geological samples and samples of marine animals, earned Nordenskjöld lasting fame at home, but its huge cost left him greatly in debt.
 Links: a. Cape Longing b. Carl Anton Larsen c. Falkland Islands d. Falkland Islands


Output: c