What does it mean if a contract is described as unenforceable?

A contract being described as unenforceable means that, while the contract may exist and have certain terms, legal enforcement of those terms through the courts is not possible. This situation often arises due to various legal principles that make it difficult to uphold the contract, such as issues with capacity, illegality, or a failure to meet statutory requirements.

The correct answer highlights that in the context of an unenforceable contract, one party may possess a justifiable reason for not complying with the terms. This scenario suggests that there are circumstances or defenses recognized by law that justify non-compliance, meaning that while the contract theoretically exists, it cannot be enforced against one of the parties because of certain valid legal excuses.

Other interpretations, such as the notion that both parties failed to comply or that the contract was executed completely, do not capture the essence of what makes a contract unenforceable. Rather, it's the absence of effective enforcement due to legal reasons that defines it. Thus, option B accurately reflects an understanding of the term "unenforceable" in contract law.