You will be given a definition of a task first, then some input of the task.
In this task, you're given a question, along with three passages, 1, 2, and 3. Your job is to determine which passage can be used to answer the question by searching for further information using terms from the passage. Indicate your choice as 1, 2, or 3.

Question: What is the focus of the subject Meissner studied on his return to Tübingen?   Passage 1:The Meskhetian Turks first arrived in Azerbaijan at the end of the nineteenth century, and more followed in 1918-1920. However, migration to Azerbaijan increased dramatically after World War II when the Soviet Union was preparing to launch a pressure campaign against Turkey. Vyacheslav Molotov, then Minister of Foreign Affairs, demanded to the surrender of three Anatolian provinces (Kars, Ardahan and Artvin); thus, war against Turkey seemed possible, and Joseph Stalin wanted to clear the strategic Turkish population situated in Meskheti, located near the Turkish-Georgian border which were likely to be hostile to Soviet intentions. Thus, in 1944, the Meskhetian Turks were forcefully deported from the Meskheti region in Georgia and accused of smuggling, banditry and espionage in collaboration with their kin across the Turkish border. Nationalistic policies at the time encouraged the slogan: "Georgia for Georgians" and that the Meskhetian Turks should be sent to Turkey "where they belong". Joseph Stalin deported the Meskhetian Turks to Central Asia (especially to Uzbekistan), thousands dying en route in cattle-trucks, and were not permitted by the Georgian government of Zviad Gamsakhurdia to return to their homeland.
 Passage 2:The ship's keel was laid down 4 January 1977 by Burrard Dry Dock at their yard in North Vancouver, British Columbia with the yard number 222. The ship was launched on 10 March 1978 and entered in Coast Guard service in March 1979. The ship was named Franklin in honour of Arctic explorer Sir John Franklin. After completing the vessel performed sea trials in the western Arctic and Northwest Passage. While transiting the Northwest Passage, heading to the icebreaker's assigned base in Newfoundland, Franklin lost a propeller in Viscount Melville Sound and was rescued by and returned to the west coast. The two ships then transited to the East Coast of Canada via the Panama Canal. In 1980, the vessel was renamed to Sir John Franklin at the request of the crew. The ship worked out of CCG Base Dartmouth and CCG Base Quebec City for most of the 1980s and 1990s, being tasked to winter icebreaking operations in the Gulf of St. Lawrence and St. Lawrence River and off Newfoundland. During the summer season, Sir John Franklin was often tasked to support the annual Arctic Summer Sealift operation for escorting cargo ships to remote port communities in the Canadian Arctic Archipelago.
 Passage 3:After Meissner’s abitur at the Humanistisches Gymnasium, in 1910, he began the study of physics and mathematics at University of Tübingen. After three terms, he went to the University of Munich as a student of the experimentalist Wilhelm Röntgen and the theoretician Arnold Sommerfeld. After one year at Munich, he returned to Tübingen to be able to study spectroscopy with Friedrich Paschen. While still a student in 1914, Meissner was able to prove the existence of oxygen lines in the solar spectrum. He was awarded his doctorate in 1915, on a thesis with the title Interferometrische Wellenlängenbestimmung im infraroten Spektralbereich. In 1916 he became an assistant to Edgar Meyer at the University of Zurich, under whom he completed his Habilitation, in 1918, with the Habilitationsschrift title Untersuchungen des Neonspektrums. The following year, he married the Polish physicist Doctor Janka Kohn.

Output:
3