MrBuyer,the Plaintiff in the Action,was Attempting to Enforce a Contract

Multiple Choice

Mr.Buyer,the plaintiff in the action,was attempting to enforce a contract in which the defendant,Mr.Seller,agreed to sell to the buyer his property,Blackacre,for $100 000.Which of the following,by itself,would be sufficient to allow Mr.Seller to get out of the contract?

A) At the time of the contract,unknown to Mr.Buyer,Mr.Seller did not understand the quality and nature of this act because of mental incapacity.
B) The $10 000 was not enough (i.e.,not fair) .
C) Although both parties agreed to this,no money had actually been paid on the contract,not even a deposit or a down payment.
D) Mr.Buyer referred to essential terms in a letter sent to Mr.Seller.
E) There was only a verbal agreement between Mr.Seller and Mr.Buyer.