Explanation:

- Priority Sector Lending (PSL) refers to the mandatory lending that banks must extend to specific sectors, like agriculture and small businesses, to ensure adequate institutional credit reaches these underserviced areas.

- Option 1: Small Industries Development Bank of India (SIDBI) - Focuses on the growth and development of micro, small, and medium enterprises. However, they don’t monitor PSL compliance in commercial banks.

- Option 2: Reserve Bank of India (RBI) - The RBI oversees and monitors the compliance of the PSL norms by banks. It sets the guidelines, targets, and sub-targets for PSL.

- Option 3: Government of India - Although the government may influence policies, it doesn't directly monitor PSL.

- Option 4: National Bank for Agriculture and Rural Development (NABARD) - Mainly caters to refinancing institutions lending to the agriculture and rural sector. It doesn’t monitor PSL compliance across all banks.