Given the task definition and input, reply with output. 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 year did Philby defect? Passage 1:The Norse-Gaelic Clan Donald traces its descent from Domhnall Mac Raghnuill (d. circa 1250), whose father Reginald or Ranald was styled "King of the Isles" and "Lord of Argyll and Kintyre". Ranald's father, Somerled was styled "King of the Hebrides", and was killed campaigning against Malcolm IV of Scotland at the Battle of Renfrew in 1164. Clan Donald shares a descent from Somerled with Clan MacDougall, who traces their lineage from his elder son, Dugall mac Somhairle. Their dynasties are together commonly referred to as the Clann Somhairle. Furthermore, they are descended maternally from both the House of Godred Crovan and the Earls of Orkney, through Somerled's wife Ragnhildis Olafsdottir, daughter of Olaf I Godredsson, King of Mann and the Isles and Ingeborg Haakonsdottir daughter of Haakon Paulsson, Earl of Orkney. It remains uncertain if the Clann Somhairle are also descendants in some manner, through one or another of the above dynasts, of the House of Ivar, but this is commonly argued.
Passage 2:In May 1986, Souther requested Soviet citizenship, aware that the investigation against him was progressing. In June, fearing imminent arrest, Souther defected to the Soviet Union by flying from the United States to Rome, where the Soviet intelligence services transferred him to Moscow. Initially, Soviet counterintelligence units were suspicious of Souther's defection and feared that he was a double agent for the CIA, but he was cleared shortly afterwards. On 2 October 1986, Souther was granted Soviet citizenship in a decree from the Presidium of the Supreme Soviet, and adopted the Russian name Mikhail Yevgenyevich Orlov. Souther was well-received by the Soviet authorities, gifting him an apartment in Moscow and a dacha on the outskirts of the city, and promoting him to the rank of major in the KGB one of few foreign spies to be commissioned as an officer in the agency. Souther became actively engaged in scientific activities, developed his own English teaching program, walked around Moscow a lot, and travelled to other Soviet cities. Souther met and befriended other foreign Soviet intelligence agents that had defected including Kim Philby and George Blake. Souther married a Russian woman named Elena, an English teacher at the Intelligence Institute, and they had a daughter named Alexandra. In early 1989, Souther was awarded an Order of Friendship of Peoples for his contributions in the intelligence services following a petition from the KGB leadership.
Passage 3:Although the UKST was originally used to take photographs of the sky, traditional photographic glass (and film) became largely superseded by large electronic CCD detectors in the late 1990s, and after 2000 the UKST was used mostly for multi-object spectroscopy with the 6 degree Field (6dF) instrument. 6dF uses a robot to position up to 150 optical fibres on a metal plate mounted at the focal plane of the UKST, which then carry light from the targets to a spectrograph which sits on the floor of the dome. The 6dF Galaxy Survey (6dFGS), a redshift survey of 120,000 infrared-selected galaxies was completed in 2005, and from 20032013 the UKST then carried out the RAdial Velocity Experiment (RAVE) to measure the radial velocities and metallicities of around to 0.5million stars in the Milky Way Galaxy.
2