Under a System of Floating Exchange Rates, Changes in the Value

Under a system of floating exchange rates, changes in the value of the U.S. dollar relative to other currencies are the result of

A) negotiated rate adjustments between the U.S. government and the World Trade Organization.
B) decisions made by the Federal Reserve Board of Governors in order to implement monetary policy.
C) fluctuations in the world price of gold.
D) changes in the supply of and/or demand for dollars in the global currency market.