Explanation:

- The Reserve Bank of India (RBI) introduced a four-tiered regulatory framework for Urban Co-operative Banks (UCBs). This aims to simplify and enhance regulatory oversight.

- Option 1: UCBs - Urban Co-operative Banks have been categorized into different tiers according to size and operations. Correct Answer

- Option 2: RCBs - Regional Co-operative Banks have distinct regulatory practices, different from UCBs.

- Option 3: Commercial Banks are not part of this specific framework.

- Option 4: RRBs - Regional Rural Banks are similarly not included in this new framework.

- Option 5: All of the above - Incorrect, as it only applies to UCBs.