Nafta established a community to promote among countries that have common economic and political interests in north america.

Trade.
   
NAFTA, or the North American Free Trade Agreement, involved the three major countries of the North American Continent, the USA, Canada, and Mexico. The main idea of the agreement was to abolish many tariffs, taxes on imported and exported products, between the US and the two other countries. Without these tariffs, products from those countries will be as competitive as their US based competition; this increases the likelihood of a company to want to business with companies and customers in the US, thus promoting trade.

The answer to the question is a.