Step 1: Understanding the Concept:
India's presence in international organizations started even before its formal independence from British rule.
Step 2: Detailed Explanation:
1. UN Founding: The United Nations was officially established on October 24, 1945.
2. India's Role: India participated in the San Francisco Conference (1945) and signed the UN Charter.
Despite being a colony, India is recognized as one of the 51 "original" founding members.
India ratified the charter on October 30, 1945.
Step 3: Final Answer:
India joined the UN in 1945. Hence, (A) is the correct option.