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: What's the average lifespan of the animal that has a jaw with properties similar to those that probably led to the evolution of baleen? Passage:The oldest true fossils of baleen are only 15 million years old because baleen rarely fossilizes, and scientists believe it originated considerably earlier than that. This is indicated by baleen-related skull modifications being found in fossils from considerably earlier, including a buttress of bone in the upper jaw beneath the eyes, and loose lower jaw bones at the chin. Baleen is believed to have evolved around 30 million years ago, possibly from a hard, gummy upper jaw, like the one a Dall's porpoise has; it closely resembles baleen at the microscopic level. The initial evolution and radiation of baleen plates is believed to have occurred during Early Oligocene when Antarctica broke off from Gondwana and the Antarctic Circumpolar Current was formed, increasing productivity of ocean environments. This occurred because the current kept warm ocean waters away from the area that is now Antarctica, producing steep gradients in temperature, salinity, light, and nutrients, where the warm water meets the cold.
 Links: a. Antarctic Circumpolar Current b. Dall's porpoise c. Salinity d. Salinity
Example Output: b

Example Input: Question: How long had Shumilov been in the military when the Soviet invaded Poland? Passage:Colonel (promoted to Major General 4 June 1940) Mikhail Shumilov took command in April 1938. In September 1939, the corps fought in the Soviet invasion of Poland as part of the 10th Army. It included the 6th, 33rd, and the 121st Rifle Divisions at the beginning of the invasion on 17 September. By 2 October, these divisions had transferred to other units, and it included the 29th, 64th, and 145th Rifle Divisions instead. The corps headquarters relocated to Grodno in November and became part of the 11th Army. Between June and July 1940 it was briefly headquartered at Kovno before moving to Šiauliai in August, part of the Baltic Special Military District. The 11th transferred to the 8th Army in October, and included the 11th and 125th Rifle Divisions by the outbreak of the war. It defended a 40-kilometer sector on the left flank of the 8th Army, with its headquarters in the forests northwest of Skaudvilė. The 125th Rifle Division was in the corps' first echelon, holding covering the highway and railroad from Tilsit to Šiauliai. The 48th Rifle Division (part of the adjacent 10th Rifle Corps), after moving forward from Riga, was to take up positions on the left of the 125th. The corps' 73rd Corps Artillery Regiment included four battalions of 107 mm guns.
 Links: a. Mikhail Shumilov b. 11th Rifle Division c. 10th Rifle Corps d. Baltic Military District
Example Output: a

Example Input: Question: How long were the Bears in the Northern League? Passage:Born in Staten Island, New York, Majeski began his professional baseball career as a second baseman in at the age of 18 with the Eau Claire Bears of the Northern League. In his second season at Eau Claire, he posted a .365 batting average to finish as runnerup in the Northern League batting championship. His performance brought him to the attention of the Chicago Cubs who signed him to a contract and sent him to play for their Minor League affiliate, the Moline Plowboys of the Three-I League. Majeski continued to perform well, winning the Three-I League batting championship with a .345 batting average. He was traded to the Birmingham Barons of the Southern Association in where he hit for a .325 average.
 Links: a. Batting average (baseball) b. Northern League (baseball, 1902–71) c. Illinois–Indiana–Iowa League d. Second baseman
Example Output:
b