Which One of the Following Mistakes Voids a Contract

Which one of the following mistakes voids a contract?

A) Two parties contract for a shipload of coal, but unknown to both parties, at the time of the contract the ship had sunk and the coal had been lost.
B) Sally and Mary had a serious misunderstanding about a term in the contract; the court found that the more reasonable interpretation was that of Sally.
C) Sam bought three gallons of paint, but found he had made a mistake; two would have been sufficient.
D) Two parties contracted for the sale and purchase of a painting for the price of $800. When the contract was written up, the price was incorrectly stated as $900.
E) When Mr. and Mrs. Houston put their property up for sale, Sam without speaking to the Houstons or their agent about the land, offered close to the asking price because he thought it was suitable for growing wheat. After his offer was accepted, he learned it was not suitable for wheat.