Ashley Contracted to Perform on Her Horse, Coronation, in the Opening

Multiple Choice

Ashley contracted to perform on her horse, Coronation, in the opening ceremonies of the World Equestrian Games. If, before the event, Coronation pulls a tendon in its leg and Ashley has to cancel her appearance, this is a case of:

A) subjective impossibility, which does not excuse Ashley from liability for breach of contract.
B) objective impossibility, which discharges Ashley's contractual duty.
C) frustation of purpose, which does not discharge Ashley's contractual duty.
D) commercial impracticability, which excuses nonperformance.