Which of the Following Best Illustrates the Double Coincidence of Wants

Which of the following best illustrates the double coincidence of wants?  

A)  Tom and Jerry would like to purchase the same good. 
B)  Tom has something he is willing to trade to Jerry, and Jerry has something he is willing to trade to Tom. 
C)  Tom and Jerry have very similar tastes, thus Tom's wants coincide with Jerry's wants. 
D)  Tom has something he is willing to trade to Jerry, who wants it, and Jerry has something he is willing to trade to Tom, who wants it.