Definition: 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.
Input: Question: What did the 390th Tactical Fighter Squadron do during the Vietnam War? Passage:Vandenberg graduated from the United States Military Academy in 1951 (where Buzz Aldrin was one of his classmates). In 1953, Vandenberg was assigned to the 86th Fighter-Bomber Wing. Later he would serve as a flight commander with the 413th Tactical Fighter Wing and the 31st Tactical Fighter Wing. He graduated from the Air Command and Staff College in 1961, after which he was assigned to the 4th Tactical Fighter Wing. In 1963, Vandenberg was appointed Operations Officer with the 23rd Tactical Fighter Squadron. During the Vietnam War, Vandenberg commanded the 390th Tactical Fighter Squadron. Upon returning stateside he was assigned to The Pentagon to work in the Office of the Director of Plans. He would graduate from the National War College in 1969 and return to The Pentagon to work with the Joint Chiefs of Staff. In 1971, Vandenberg became commander of the 12th Flying Training Wing. Vandenberg was named Vice Commandant of Cadets at the United States Air Force Academy in 1972. He would serve as Commandant from 1973 to 1975, during which time he assumed the rank of brigadier general. From 1976 to 1979, Vandenberg served at Headquarters U.S. Air Force, first as Deputy Director of Plans, later as Director of Operations and Readiness, and finally as Assistant Deputy Chief of Staff for Operations, Plans, and Readiness. Vandenberg was ultimately named Vice Commander in Chief of the Pacific Air Forces. His retirement was effective as of January 1, 1981.
 Links: a. Buzz Aldrin b. 390th Electronic Combat Squadron c. Joint Chiefs of Staff d. Vietnam War
Output:
b