What gives courts the power to declare actions of congress, the president, or state officials unconstitutional?

Foreign exchange market by business & economics research advisor, from the library of congress in 1971, u.s. dollars were no longer exchanged for gold; and in 1973, the floating exchange rate system that governs the fx market today was put into place. now, all currencies are valued by the market forces of supply and demand. since the abandonment of the gold standard, the fx market has become an important part of international economics. with the advent of floating exchange rates, the foreign exchange market has become unregulated. no institution sets rules for trading, and it is not under the supervision of any international organization. when necessary, governments and central banks often work together to restore stability to the fx market. foreign exchange and international trade are closely connected. together, they affect the economic situation of people throughout the world.currently, the foreign exchange rate for all world currencies is a) a fixed exchange rate, based on the u.s. dollar. b) a floating exchange rate, based on the u.s. dollar. c) a fixed exchange rate, based on market forces of supply and demand. d) a floating exchange rate, based on market forces of supply and demand.the right answer is d) a floating exchange rate, based on market forces of supply and demand.