Choice "B" is correct. A third party may withdraw from a transaction or agreement entered into with an agent who exceeded his or her authority at any time prior to the principal's ratification of the agent's unauthorized acts. In this case King notified Maple of King's withdrawal from the agreement on May 1, six days before Maple's attempted ratification on May 7. Therefore, Maple's action will fail.
Choice "c" is incorrect. An unauthorized transaction or agreement can be ratified only before the third party to the transaction or agreement withdraws. Here, King withdrew before Maple ratified.
Choice "d" is incorrect. An unauthorized transaction or agreement can be ratified only if the agent without authority claimed to be acting on behalf of the principal, but knowledge of the principal's capacity does not prevent the third party from withdrawing once the third party learns that the transaction or agreement was unauthorized.
Choice "a" is incorrect. An unauthorized transaction or agreement by an agent is voidable by the third party if the third party cancels the tranaction or agreement prior to the principal's ratifying the transaction or agreement. Because the principal may ratify (before the third party cancels) the transaction or agreement, the transaction or agreement is not void.