B

Explanation:

A contract for an illegal purpose, such as the sale of heroin, is void because it violates public policy and legal statutes. A void contract has no legal effect and cannot be enforced by either party. Option A (quasi contract) is incorrect, as quasi contracts are implied by law to prevent unjust enrichment, not applicable here. Option C (voidable contract) is incorrect, as voidable contracts are valid but can be canceled by one party, which does not apply to illegal agreements. Option D (secondary party beneficiary contract) is irrelevant, as it involves third-party rights, not illegal activities. The answer “B” aligns with the legal principle that contracts for illegal purposes are void.