Answer:
WTO - The main function of the WTO is to promote international trade among member nations, by developing guidelines, policy recommendations, and common agreements that foster global exchange of goods and services.
OPEC - The main function of the OPEC is to reach price agreements of oil among the member nations, which are the most important producers of oil in the world, except of the U.S., which is not a member nation.
IMF - The main function of the IMF is to ensure global financial stability, to help member nations with currency crisis, and balance of payments crisis, and to develop studies, statistics, and policy recommendations for member nations.
World Bank - The main function of the WB is to promote sustainable development around the world. This is why the WB is mainly in charge of giving low-interest loans to developing nations.
European Union - The European Union is a monetary and economic union among 26 member states. The European Union coordinates issues across member states on monetary policy, trade policy, general economic policy, and even immigration policy.