Explanation:

- Option 1: MSP (Minimum Support Price)

- Correct Answer

- It is a government assurance to farmers that their produce will be purchased at a specified price. This ensures a minimum profit to the farmers and reduces their risk.

- Option 2: MRP (Maximum Retail Price)

- It is the maximum price at which a product can be sold to consumers. It is unrelated to government purchases from farmers.

- Option 3: Both a and b

- Incorrect because MRP is not related to government buying farmers' produce.

- Option 4: None of these

- Incorrect as MSP is the correct assurance mechanism.