22.Under the commercial frustration doctrine, performance is excused when:

Select one:

a. statutes and legislation make the performance more difficult.

b. something that is essential to the promisor's performance is destroyed through no fault of the promisor, but its substitute is available.

c. events occur after the formation of the contract that would make the return performance of the other party worthless to the promisor.

d. the promisor impliedly assumes the risk that the event would occur.