Mutual mistake doctrine: If both parties share a material mistaken belief about a fact at the time of contracting, the contract may be rescinded; if the risk is allocated to a party, rescission is not available.

• A. If both parties share a material mistaken belief about a fact at the time of contracting, the contract may be rescinded.
• B. If both parties share a material mistaken belief about a fact at the time of contracting, the contract may be rescinded; if the risk is allocated to a party, rescission is not available.
• C. A unilateral mistake by one party allows rescission if the other party knew of the mistake.
• D. Mutual mistake always allows rescission.

Answer: (B)