The correct answer is option 1: 1950. The provisions of citizenship in the Indian Constitution became applicable in 1950. It is important to note that the Indian Constitution was adopted and came into effect on January 26, 1950. This date is significant because it marks the transition of India from a British Dominion to a republic. With the adoption of the Constitution, citizenship provisions were put in place to define who would be considered a citizen of India. These provisions lay down the qualifications, rights, and obligations of Indian citizenship. Therefore, it is accurate to say that the provisions of citizenship in the Indian Constitution became applicable in 1950.