You will be given a definition of a task first, then some input of the task.
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.

Question: How many groups were there in the Fighter Command? Passage:At the start of the Second World War before the US entered the war, there were a large number of American volunteers offering their services. No. 71 was formed at RAF Church Fenton on 19 September 1940 with Brewster Buffalos. Appraisal by Royal Air Force acceptance personnel criticised the Brewster Buffalo on numerous points, including lack of armament and pilot armour, poor high-altitude performance, engine overheating, unreliability and cockpit controls, while it was praised for its handling, roomy cockpit and visibility. The aircraft were deemed unsuitable for European conditions and Hawker Hurricanes replaced them from November 1940. The squadron became operational at RAF Kirton-in-Lindsey on 5 February 1941 and moved in April to RAF Martlesham Heath in Suffolk for operations over Europe. During May, it suffered its first loss when Mike Kolendorski was killed during a fighter sweep over the Netherlands. The intensity of operations stepped up with a move into No 11 Group of Fighter Command, being based at RAF North Weald in Essex by June 1941. On 2 July, William J. Hall became the first Eagle Squadron pilot to become a Prisoner of War (POW) when he was shot down during an escort mission. The squadron's first confirmed victory came on 21 July 1941 during a bomber escort mission, when Pilot Officer William R. Dunn destroyed a Messerschmitt Bf 109F over Lille. In August, the Spitfire Mk II replaced 71 Squadron's Hurricanes, before the squadron quickly re-equipped with the latest Spitfire Mk VB. The unit soon established a high reputation, and numerous air kill claims were made in RAF fighter sweeps over the continent during the summer and autumn of 1941. In December, the Squadron was rested back at Martlesham Heath, before a move to Debden in May 1942. When informed of the attack on Pearl Harbor, most of the Eagle Squadron pilots wanted to immediately join the fight against Japan. Representatives from 71 and 121 Squadrons went to the American Embassy in London and offered their services to the United States. The pilots from 71 Squadron decided they wanted to go to Singapore to fight the Japanese and a proposal was put to RAF Fighter Command, but it was turned down. On 29 September 1942 the squadron, together with the other two Eagle squadrons, was transferred to the US Army Air Forces, becoming the 334th Fighter Squadron of the 4th Fighter Group.
 Links: a. United States Army Air Forces b. William R. Dunn c. RAF Fighter Command d. United States Army Air Forces
Output:
c