Instructions: 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: How long had Juan Carlos Onganía been leading Argentina by the year La balsa was written? Passage:"La balsa" (; Spanish for "the raft") is the debut single by the Argentine band Los Gatos, released on July 3, 1967 on Vik, a subsidiary of RCA Victor. Formed in 1967 after the disbandment of Los Gatos Salvajes, Los Gatos were the house band of the bar La Cueva, which became a popular meeting place for rock enthusiasts and the birthplace of Argentine rock—known locally as rock nacional (Spanish for "national rock"). During the mid-to-late 1960s, Buenos Aires was experiencing a cultural blossoming characterized by innovations in modern art, literature and cinema, largely driven by a burgeoning youth subculture that adhered to the countercultural phenomenon of the decade. The underground had its center in La Cueva, Plaza Francia and the Torcuato di Tella Institute, and identified with British Invasion music and the sexual revolution. "La balsa" was written by Litto Nebbia—lead vocalist of the band—and Tanguito (credited as Ramsés) on May 2, 1967, in the men's toilet of La Perla de Once, another bar frequented by the group. At the time, Argentina was under a military dictatorship led by Juan Carlos Onganía, which regularly imprisoned and persecuted these young bohemians.
 Links: a. British Invasion b. Juan Carlos Onganía c. Argentine rock d. Tanguito
Output:
b