Many People Sell Goods Through EBay at Prices That Are

Many people sell goods through eBay at prices that are higher than the prices they paid for these goods.Economists consider these transactions as

A) examples of zero-sum games, since the value of the goods sold is exactly equal to the prices paid for them.
B) unproductive since the goods sold have been produced in the past.
C) examples of exploitation of buyers of the goods by the sellers.
D) examples of arbitrage.