Explanation:

- Option 1: Liquid

- This refers to assets that can be easily converted into cash. It's not related to assets that have been substandard for a long duration.

- Option 2: Non-performing

- Non-performing assets are loans or advances where the borrower hasn't made scheduled payments for over 90 days. However, it's a broader category that includes substandard, doubtful, and loss assets.

- Option 3: Doubtful

- Correct Answer: Assets that remain substandard for 12 months often become doubtful. This indicates a serious credit risk, but recovery is still possible.

- Option 4: Loss

- These assets are considered uncollectible and need to be entirely written off, although there might be some negligible recovery in the future.