Which of the Following Is an Example of Barter Where

Which of the following is an example of barter where the double coincidence of wants may NOT always occur?

A) An individual uses tobacco to buy everything, and tobacco is an item that all merchants willingly accept.
B) An individual uses fiat money to buy everything, and fiat money is an item all merchants willingly accept.
C) An individual wants to buy a new set of tires using seashells from a merchant who needs seashells.
D) All merchants price goods in terms of number of seashells.
E) All merchants price goods in terms of amount of fiat money.