The correct answer is option 1 - 1956. In 1956, the unification of Karnataka was achieved through the States Reorganization Act. Before the unification, the region that now constitutes Karnataka was divided into various princely states and territories, including Mysore State, Coorg State, and Bombay-Karnataka region. However, as a result of the States Reorganization Act, these different territories were merged to form the state of Mysore on November 1, 1956. The name of the state was later changed to Karnataka in 1973. Therefore, it was in the year 1956 that the unification of Karnataka took place.