(C) Reserve Bank of India
The Reserve Bank of India (RBI) controls the issuance of currency notes on behalf of the Central Government and supervises/regulates the credit system in India.
The RBI is India's central bank. The textbook (Chapter 3 – Money and Credit) clearly states that the RBI supervises the functioning of formal sources of loans and monitors banks in maintaining cash balances. Punjab National Bank, Indian Bank, and State Bank of India are commercial banks — they operate under RBI's regulation, not as regulators themselves.