Currency Trading Time Zones

Do u know economic good.. u should help me with this quick questions …economic question?
The —— determines how much a foreign currency is worth in a certain nation.
i have to pick one of these words to fit it.
here are the words;
comparative advantage
appreciation
exchange rate
exports
free-trade zone
imports
infant industry
protectionism
tariff
trade surplus
depreciation
please no rude answers dont got time for it at all.
exchange rate
comparative advantage- relates to producing goods
appreciation- is about increasing the value of something
exchange rate- is how much currency is bought and sold for
exports- is goods sold abroad
free trade zone- is where there are no tariffs/taxes etc when trading with other countries in the FTZ
imports- are goods bought from abroad
infant industry- new industry
protectionism- protecting home produced goods by putting tariffs etc on imports
tariff- like a tax on imports, makes them more expensive
trade surplus- overtrading
depreciation- a decrease in value
Trading the Australian Dollar $AUDUSD 4am NEW YORK Time Zone 25th June 2010