Which of the Following Contracts Is Void for Common Mistake

Which of the following contracts is void for common mistake?

A) Peter plans to attend an electronics convention in Hull and books a weekend stay at the Goodnight Hotel. When he arrives in Hull, he discovers the convention had been cancelled before he made his booking.
B) Roger lives in his aunt's apartment. When she dies, her daughter agrees to sell the apartment to Roger. Unknown to both of them, the aunt has bequeathed the property to Roger in her will, but this will only surfaces after Roger and the daughter have contracted.
C) Quentin buys tickets to a concert in London taking place next week. The following day, the concert hall burns down.