Which of the Following Contracts May Be Set Aside for Mistake

Which of the following contracts may be set aside for mistake or frustration?

A) Pam sold a computer for cash to a person she mistakenly thought she had known in high school.
B) Pam enters into a contract to sell a colt to Dave, but neither party realizes that Pam has already sold the same colt to Donna.
C) Pam rented a cottage to Dave for a summer for $5000, and Pam later learns that because of winter storms, it will unexpectedly cost her $30 000 to repair the cottage so that it meets the needs of the rental contract.
D) Pam said nothing about the quality and history of a painting that she sold to Dave, despite knowing that he incorrectly believed the painting was worth more than its purchase price.
E) none of the above