Duress involves coercion or threats that force a party to enter into a contract against their free will. The correct answer is B) Duress.
Contracts entered into under duress are generally considered voidable by the party who was subjected to the duress. The affected party has the option to either void the contract or affirm it, depending on the circumstances.
The other options, such as mutual mistake, unilateral mistake, and innocent misrepresentation, may render a contract voidable, but they are not as consistently and universally applicable as duress in leading to the contract being voidable.
Therefore, the correct answer is B) Duress.
