The correct answer is C. 1961.
Goa was a Portuguese colony for over 450 years, from 1510 to 1961. On December 19, 1961, the Indian Armed Forces invaded Goa and the other Portuguese territories of Daman and Diu. The Portuguese surrendered on December 20, 1961, and Goa was integrated into India on December 26, 1961.
Option A is incorrect because 1960 was the year that the States Reorganisation Act was passed, which reorganized the states of India.
Option B is incorrect because 1681 was the year that the Portuguese captured the Maratha fort of Ponda, which gave them control of most of Goa.
Option D is incorrect because 1569 was the year that the Portuguese established their first permanent settlement in Goa.