Explanation:

- Statutory Liquidity Ratio (SLR): This is the percentage of net demand and time liabilities that a bank must maintain in the form of liquid cash, gold, or other securities. It is not kept with RBI but in the bank itself.

- Deposit Ratio: This is not a standard term in banking regulations related to RBI. It may refer to various other ratios banks maintain internally.

- Cash Reserve Ratio (CRR): This is the percentage of a bank's total deposits that must be kept in reserve with the RBI in the form of cash. It is used to ensure liquidity and control over the money supply.

- Legal Reserve Ratio: This term is not used specifically in Indian banking, but may be used interchangeably with CRR or SLR in different contexts.

Correct Answer: Option 3, Cash Reserve Ratio (CRR).