Step 1: Control of banking system.
The Reserve Bank of India (RBI) is the central bank of the country and regulates all commercial banks.
Step 2: Role of RBI.
RBI controls monetary policy, supervises lending, deposits, and overall functioning of commercial banks.
Step 3: Analyzing options.
(A) Government of India – Incorrect, it frames policies but does not directly control banks.
(B) State Bank of India – Incorrect, it is only one bank, not a regulator.
(C) NABARD – Incorrect, it focuses on rural/agricultural credit.
(D) Reserve Bank of India – Correct, regulator of all banks.
Step 4: Conclusion.
Hence, commercial banks are controlled by the Reserve Bank of India.