Q.Name the contract which is forbidden by law.

The answer is option (d); a void agreement means an agreement not enforceable by law.

Under the Indian Contract Act, 1872:

• Section 2(g) defines a void agreement as "an agreement not enforceable by law." It is void from the start (void ab initio) and creates no legal rights or obligations — for example, an agreement without consideration or one made with a minor. …

The correct answer is (c) Illegal contract. A contract that is forbidden by law is an illegal contract.

In the Tamil Nadu HSC Commerce syllabus, contracts are classified by their enforceability/validity:

• Illegal contract — one whose object or consideration is unlawful/forbidden by law (for example, an agreement to commit a crime). It is void from the very beginning and not enforceable; collateral agreements to it are also affected. This matches the question, so (c) is correct.
• Valid contract — one that fulfils all essentials of a contract and is fully enforceable. …