Identify the Exception in One of the Following Situations,whereby the Contract

Identify the exception in one of the following situations,whereby the contract is discharged by frustration.

A) Rudolph is due to appear in a local variety theatre that has just been destroyed in a fire of unknown origin.
B) 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.
C) Jack contracts with Bill to build a barn on his one-hectare lot,but before the permit is obtained,a new law prohibits barns on less than three hectares.
D) Gregory,a trucker with whom you contracted last month to haul potatoes tomorrow,phones to tell you that his truck has broken down.
E) 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.