Concept:
Fundamental Duties (Article 51A) are the moral obligations of all citizens to help promote a spirit of patriotism and uphold the unity of India.
Step 1: Distinguishing duties from Directive Principles.
Promoting international peace and security is a Directive Principle of State Policy (Article 51), not a Fundamental Duty of the individual citizen.
Step 2: Verifying other options.
Options (B), (C), and (D) are explicitly listed under Article 51A as duties of citizens.
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Article 51 = Directive Principle (Not a Duty)
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to promote international peace and security
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