The correct answer is indeed option 4, "to leave it unchanged."

This can be understood through the nature of the monetary transaction in question - withdrawing money from a bank account.

Option 1 suggests that the money supply would decrease by Rs 1,00,000. This is incorrect. When you withdraw money from your demand deposit account, it does not leave the economy. Instead, it is simply changing forms - from a bank deposit to cash.

Option 2 and 3 propose that the money supply will increase. Both of these are incorrect. Since the money is not newly created or added to the economy (it was already in the bank), the aggregate money supply doesn`t increase.

When you withdraw money, it is simply a transfer of funds from your bank account to your hands. No new money is created or destroyed, so the total money supply within the economy remains the same - hence option 4 is correct. This demonstrates that it`s crucial to understand the flow of money in any economic transactions to determine the overall impact on the monetary supply.