Explanation:

- Option 1: Money lenders

- Typically, these are individual lenders.

- They are considered non-institutional sources.

- Often associated with high-interest rates.

- Option 2: Landlords

- They might provide credit informally.

- Also fall into the category of non-institutional sources.

- Historically known for less formal arrangements.

- Option 3: Regional Rural banks

- Institutional source of rural credit.

- Established to provide banking services in rural areas.

- Regulated by the government and adhere to formal banking practices.

- Option 4: None of these

- Incorrect, as Regional Rural banks are an institutional source.