Explanation:

- RBI (Option 1): The Reserve Bank of India primarily regulates the banking system. It plays a role in the financial markets but is not a direct regulator of capital markets.

- SEBI (Option 2): The Securities and Exchange Board of India is the main regulator for capital markets in India. It oversees stock exchanges and protects investor interests.

- Ministry of Finance (Option 3): While it influences financial policies and frameworks, it does not directly regulate capital markets like SEBI does.

- IRDA (Option 4): The Insurance Regulatory and Development Authority of India governs the insurance industry. It does not regulate capital markets.

- The correct answer is Option 4: IRDA.