Which one of the following activities of the Reserve Bank of India is considered to be part of 'sterilization'?

1. Sterilization refers to the monetary policy actions taken by a central bank (like the Reserve Bank of India) to counteract the effects of foreign exchange interventions on the domestic money supply. 2. When the RBI buys foreign currency, it injects rupees into the banking system, increasing liquidity. To neutralize this ('sterilize' it), the RBI sells government securities through Open Market Operations (OMO), absorbing the excess rupees. 3. Conversely, if the RBI sells foreign currency, it withdraws rupees, decreasing liquidity. To sterilize this, it might buy government securities through OMO. 4. Therefore, conducting 'Open Market Operations' is the primary tool used by the RBI for sterilization. 5. Options (B), (C), and (D) represent other important functions of the RBI (oversight of settlement and payment systems, debt and cash management for governments, regulating NBFIs), but they are not considered part of sterilization.