Answer: USS Saratoga
Despite being the oldest US carrier remaining after 1942, Saratoga played a major role throughout the Pacific War. She required repairs in the first half of 1942 after being torpedoed by a Japanese submarine, becoming the new flagship of Admiral Fletcher following the Battle of Midway, and saw service during the campaign for Guadalcanal and the Solomon Islands, being retained in the South Pacific throughout 1943, and again, following refit, in 1944. Saratoga was eventually withdrawn from operations in March 1945, owing to the number of more modern ships, and was used as a training ship for the remainder of the war. After the war's end, the ship was used as part of Operation 'Magic Carpet', the mission to repatriate US servicemen from all theaters, before being assigned as a target vessel in Operation 'Crossroads', an series of atomic bomb tests. Saratoga was eventually sunk in the second 'Crossroads' test on 25 July 1946, and was officially decommissioned on 15 August the same year.
Of the other two pre-war ships to survive the war, Ranger was assigned as a training carrier in the Atlantic Fleet in January 1944, before transiting to the Pacific in July. She remained in this role until the end of the war before returning to the Atlantic, where she was finally decommissioned on 18 October 1946, before being sold for scrap on 31 January 1947. Enterprise's war service became legendary, as she was the most decorated ship in the US Navy by the end of the war, having seen combat in almost every major action in the Pacific. Assigned to Operation 'Magic Carpet', she transferred to the Atlantic in September 1945, making three voyages to and from Europe before being decommissioned on 17 February 1947. Despite efforts to preserve her, Enterprise was eventually sold for scrap on 1 July 1958.