Which one among the following is a fundamental duty of citizens under the Constitution of India ?

Under Article 51A of the Constitution of India, which was added by the 42nd Amendment Act in 1976, there are currently 11 Fundamental Duties for citizens [3]. Clause (d) of Article 51A explicitly states that it is the duty of every citizen 'to defend the country and render national service when called upon to do so' [2]. Regarding the other options, protecting monuments of national importance is a Directive Principle of State Policy under Article 49, rather than a Fundamental Duty of citizens. Providing friendly cooperation to neighboring countries is related to the State's duty under Article 51 (Promotion of international peace and security), and knowing more about history is not a specifically listed constitutional duty. Thus, only option 3 aligns with the prescribed list of Fundamental Duties [1].

Sources

1. [1] Introduction to the Constitution of India, D. D. Basu (26th ed.). > Chapter 8: FUNDAMENTAL RIGHTS AND FUNDAMENTAL DUTIES > Fundamental Duties. > p. 161
2. [3] https://legalaffairs.gov.in/sites/default/files/(V)Effectuation%20of%20Fundamental%20Duties%20of%20Citizens.pdf
3. [2] https://dsel.education.gov.in/sites/default/files/Fundamental-Duties-English.pdf