When the President of India resigns he/she addresses resignation letter to: 

Correct option is C

The correct answer is (c) The Vice President of India. According to Article 56(1)(a) of the Indian Constitution, if the President of India wishes to resign, he or she must submit the resignation letter to the Vice President. This procedure is in place because the Vice President is the immediate successor to the President’s office in case of resignation, removal, or death.
Key Points:
1. Article 56 specifies the terms, tenure, and resignation process for the President of India.
2. The Vice President serves as the ex-officio chairperson to receive the President’s resignation, ensuring continuity.
3. In the event of a President's resignation, the Vice President temporarily assumes the President's duties until a new President is elected.
4. The Prime Minister, Chief Justice of India, and Attorney General have no constitutional role in accepting or processing the President’s resignation.
5. The resignation process ensures a clear chain of command, which maintains stability in the highest office.