In All but One of the Following Situations,the Contract Is

In all but one of the following situations,the contract is frustrated.Identify the exception.

A) Jack contracts with Bill to build a barn on his one-acre lot, but before the permit is obtained, a new law prohibits barns on less than three acres.
B) Rudolph is due to appear in a local variety theatre that has just been destroyed in a fire of unknown origin.
C) Frank has contracted to ride Emperor, a prize horse, in the Canada Day races on July 1, but on June 28 the horse breaks a leg and has to be destroyed.
D) Jerry, a doctor, is due to perform a heart transplant operation on Mary, and the night before the surgery his arthritis becomes so painful that he cannot hold a scalpel.
E) Gregory, a trucker with whom you contracted last month to haul potatoes tomorrow, phones to tell you that his truck has broken down.