A void agreement is defined as an agreement that is not legally binding or enforceable in a court of law. This means that the parties involved cannot seek any legal remedy if the terms of the agreement are breached. The correct answer is (d) Not enforceable in a court of law.

Reasons for void agreements:
1. Lack of essential elements: A valid contract must have specific essential elements such as offer, acceptance, consideration, and intention to create legal relations. If any of these elements is missing, the agreement becomes void.

2. Illegal subject matter: If the subject matter of the agreement is illegal, such as an agreement to commit a crime, the agreement is void.

3. Incapacity of parties: If one or both parties are incapable of entering into a contract (e.g., minors, persons of unsound mind, or intoxicated persons), the agreement is void.

4. Mistake of fact: If both parties are under a mistake of fact essential to the agreement, the agreement is void. For example, if both parties believe they are contracting for the sale of a specific car, but the car has already been destroyed, the agreement is void.

5. Fraud, misrepresentation, or undue influence: If a party enters into an agreement due to fraud, misrepresentation, or undue influence by the other party, the agreement is void.

6. Impossibility of performance: If the performance of the agreement becomes impossible due to unforeseen events or circumstances, the agreement is void. For example, if the contract is for the delivery of goods and the goods are destroyed before delivery, the agreement becomes void.

7. Violation of public policy: If the agreement is contrary to public policy or the law, it is void. For instance, an agreement to restrain trade or restrict personal freedom is void.

In summary, a void agreement is not legally enforceable, and the parties involved cannot seek legal remedies in case of a breach. This is mainly due to the lack of essential elements, illegality, incapacity, mistake, fraud, impossibility, or violation of public policy.