The correct answer is C) eliminating barriers to trade benefits the economies of member nations.
Barries to trade can be monetary, but they can also be in form of permission on import and export of certain goods. If the countries, companies and producing individuals know reliably that they will be able to sell good to the other countries without problems such as embargos, they will more likely invest into their plans, which is just one of the many ways in which the trade blocks benefit the local economies.
