The "coincidence of wants" problem associated with barter refers to the fact that

A) for exchange to occur, each seller must have a product that some buyer wants.
B) money must be used as a medium of exchange or trade will never occur.
C) specialization is restricted by the size or scope of a market.
D) buyers in resource markets and sellers in product markets can never engage in exchange.

The "coincidence of wants" problem in barter arises because without a medium of exchange, each buyer and seller must have a product that the other party wants. This can make exchange difficult, inefficient, and sometimes even impossible. Money, as a medium of exchange, helps solve this problem by facilitating transactions between buyers and sellers with different wants and needs. Option B is incorrect because while money is a solution to the coincidence of wants problem, it is not the only solution. Option C is incorrect because specialization is not directly related to the coincidence of wants problem. Option D is incorrect because buyers and sellers in resource markets and product markets can engage in exchange, provided there is a demand for the resource/product and a mutually acceptable price.