Choice "D" is correct. The concept of balance of power anticipates that no one nation will dominate or interfere with the activities of others.
Choice "c" is incorrect. Self regulation of exchange rates through supply and demand for currency contributes to maintaining economic balance of power, however means of exchange do not require floating exchange rates.
Choice "b" is incorrect. The concept of a global balance of power does not anticipate consistent dominance by any one nation or group of nations.
Choice "a" is incorrect. Self regulation of trade balances (net imports and net exports) contributes to a global economic balance of power, however trade balances need not entirely self regulate to ensure the balance of power.