Explanation:

- Statutory Audit: This is a mandatory audit required by law. Banks must undergo statutory audits to ensure compliance with financial regulations.

- Balance Sheet Audit: Focuses on verifying the accuracy of the bank's balance sheet, ensuring that assets and liabilities are reported correctly.

- Concurrent Audit: An ongoing audit process that examines financial transactions as they occur. It helps detect errors or fraud in real-time.

- All of the above: Audits of banks can fall into all these categories, as banks are subject to statutory requirements, need balance sheet accuracy, and benefit from concurrent checks.