Introduction:
When all the banks in an economy are nationalized and converted into a monopoly bank, there are certain implications for the total deposits in the economy. Let's analyze the possible outcomes and explain why the correct answer is option 'C'.

Explanation:
1. Consolidation and Centralization:
- When all banks are nationalized and merged into a single monopoly bank, there is a consolidation and centralization of banking operations.
- This means that all the deposits that were previously held by different banks are now under the control of the monopoly bank.

2. No Change in Total Deposits:
- The total deposits in the economy will neither increase nor decrease as a result of nationalizing and converting banks into a monopoly bank.
- While the ownership and control of the banks change, the total amount of deposits remains the same.
- Nationalization does not affect the actual amount of money deposited by individuals, businesses, or other entities.

3. Impact on Deposit Holders:
- For the deposit holders, there may be a change in the name and ownership of the bank where their deposits are held.
- However, the deposits themselves remain intact and unaffected.
- Deposit holders can continue to access their funds and utilize banking services as usual.

4. Benefits of Nationalization:
- The nationalization of banks and the creation of a monopoly bank can have certain benefits for the economy.
- It allows for better regulation and control over the banking sector, reducing the risk of financial instability.
- The government can implement policies and direct lending to specific sectors to promote economic growth and development.
- Nationalization can also ensure that banking services are provided to all sections of society, including those who may have been previously excluded.

Conclusion:
When all the banks in an economy are nationalized and converted into a monopoly bank, the total deposits in the economy would neither increase nor decrease. While there would be changes in ownership and control, the actual amount of money deposited by individuals and entities remains the same.