All of the Following Except One Explain Why the Purchasing

All of the following except one explain why the purchasing power theory does not hold in the real world.Which is the exception?

A) Most personal services cannot be traded between countries.
B) There are costs of transportation involved in international trading,and differences in these costs may persist.
C) Some products are more expensive to produce in one country than in another.
D) Tariffs and quotas alter the prices of products and affect the free trading of products.
E) Consumers in different countries sometimes have different preferences.