Explanation:

- Valid Contract: A straightforward agreement where A agrees to buy B's horse for a specified price of Rs 5,000. All essential elements of a valid contract, like offer, acceptance, lawful consideration, and intent to create legal relations, seem to be present. Correct Answer.

- Contingent Contract: This is a contract dependent on the occurrence or non-occurrence of an uncertain event. There’s no indication of such a condition here, so this option doesn't apply.

- Not a Contingent Contract: More appropriate for options indicating whether a contract relies on other conditions. The agreement here isn’t contingent.

- Void Agreement: An agreement without legal effect. There's no reason to assume this horse sale lacks legality or enforceability.