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 wide is the body of water that separates the Eurasian and North American continents? Passage:The Russian Empire began its interest of the Pacific Northwest in the 18th century, initially curious if there was a land connection between the Eurasian and North American Continents. Two expeditions were led by Vitus Bering, with the findings proving the separation of two continents through the Bering Sea. Being the first European nation to chart much of what comprises the modern American state of Alaska, many locations retain Russian place names. The discovery of sizable fur bearing populations by Bering drew the attention of promyshlenniki previously engaged in the Siberian fur trade. Based out of the Siberian ports of Okhotsk or Petropavlovsk, fur trappers sailed and reported the location of land formations like the Aleutian Islands, Kodiak Island and portions of the Alaskan mainland. Relations with Native Alaskans was often terse due to the uncontrolled actions of particular promyshlenniki who killed and raped Indigenous on islands they trapped furs.
Links: a. Bering Sea b. Siberia c. Russian Empire d. Bering Sea

Output: a

Input: Consider Input: Question: How deep were their heavy infantry formations normally? Passage:Having recovered from their losses at Trebia (218 BC) and Lake Trasimene (217 BC), the Romans decided to engage Hannibal at Cannae, with approximately 86,000 Roman and allied troops. They massed their heavy infantry in a deeper formation than usual, while Hannibal used the double envelopment tactic and surrounded his enemy, trapping the majority of the Roman army, who were then slaughtered. The loss of life on the Roman side was one of the most lethal single day's fighting in history; Adrian Goldsworthy equates the death toll at Cannae to "the massed slaughter of the British Army on the first day of the Somme offensive in 1916." Only about 15,000 Romans, most of whom were from the garrisons of the camps and had not taken part in the battle, escaped death. Following the defeat, Capua and several other Italian city-states defected from the Roman Republic to Carthage.
Links: a. Cannae b. Adrian Goldsworthy c. Heavy infantry d. City-state

Output: c

Input: Consider Input: Question: What country claims ownership of the place Gill calculated the distance of Mars' approach? Passage:It would seem that Gill's interests lay elsewhere since after a few years he sold the business, and then spent time equipping Lord Lindsay's private observatory at Dun Echt, Aberdeenshire. In 1874, Gill joined the expedition to Mauritius to observe the transit of Venus. Three years later he went to Ascension Island to observe a near approach of Mars and to calculate its distance. While carrying out these laborious calculations, he was notified of his appointment to the Cape Observatory, which, over the following 27 years he was to refurbish completely, turning it into a first-rate institution. Gill was a meticulous observer and had a flair for getting the best out of his instruments. His solar parallax observations with a heliometer and his calculations of distances to the nearer stars, are testimony to his outstanding work. He recruited Robert Innes to the Cape Observatory.
Links: a. Robert T. A. Innes b. Dunecht c. Transit of Venus d. Ascension Island
Output: d