Which of the Following Would Immediately Let You Know That

Which of the following would immediately let you know that your existing contractual obligations have come to an end as a result of the doctrine of frustration?

A) An unforeseen occurrence caused subsequent initiation of legal proceedings.
B) An unanticipated event rendered discharge of duties functionally unrealistic.
C) An unanticipated event has caused a protracted delay in performance.
D) An unforeseen dispute over quantum has rendered performance impossible.