Bonnie Contracts to Deliver a Crop of Soybeans to Farmers

Bonnie contracts to deliver a crop of soybeans to Farmers Co-op.A tornado destroys the crop on her farm.The buyer insists that she deliver by acquiring soybeans on the open market.She claims that this is prohibitively expensive.Her best argument against enforcing the contract is

A) frustration of purpose.
B) objective impossibility of performance.
C) anticipatory repudiation.
D) commercial impracticability.