You and a Friend Run into Each Other on the Street,and

You and a friend run into each other on the street,and you see that he is carrying a fish that he has just caught.You would love to get that fish home and cook it to make your wife happy.You and your friend agree that the fish is equivalent to the corn you are carrying in your bag.The two of you then exchange the fish for the corn before heading off to your respective homes.What is this an example of?

A) authority ranking
B) communal sharing
C) market pricing
D) equality matching
E) big-gun diplomacy