With Regard to International Trade,what Is the "Law of One

With regard to international trade,what is the "law of one price"?

A) The price of labour,measured in terms of its opportunity cost,is the same in all markets.
B) The price of a product is always equal to the absolute cost of the resources that went into its production in any country.
C) The price of a product worldwide is always equal to the cost of production from the country with the lowest opportunity cost to make the product.
D) The price of a product that is costless to transport will be the same in all markets.
E) The price of natural resources is the same in all markets.