Option 1 -> India gained independence from British rule, but Portuguese territories were not included.
Option 2 -> India became a Republic, but Goa remained under Portuguese control.
Option 3 -> Goa was still a Portuguese colony at this time.
Option 4 -> Operation Vijay was launched in December 1961, liberating Goa, Daman & Diu from 451 years of Portuguese rule.
Hence, Option 4: 1961 -> The Indian Armed Forces conducted Operation Vijay on 17-19 December 1961, after which Goa, Daman and Diu were incorporated into India as a composite Union Territory -> correct