The correct answer is C. Paris.
UNESCO, or the United Nations Educational, Scientific and Cultural Organization, is a specialized agency of the United Nations headquartered in Paris, France. It was founded on 16 November 1945, and its stated purpose is to contribute to peace and security by promoting collaboration among nations through education, science, and culture in order to further universal respect for justice, for the rule of law and for human rights and fundamental freedoms for all without distinction as to race, sex, language, or religion.
UNESCO’s headquarters is located in the Place de Fontenoy in the 7th arrondissement of Paris. The building was designed by the French architect Marcel Breuer and was completed in 1958. It is a UNESCO World Heritage Site.
The other options are incorrect. New Delhi is the capital of India. London is the capital of the United Kingdom. New York is the most populous city in the United States.