The correct answer is C) Canada.
Canada is the United States largest trading partner.
Canada is a priority in trade for the United States. It is the major largest trading partner. That was one of the reasons to form the most important free trade agreement in the world between the United States, Canada, and Mexico. Called the North America Free Trade Agreement NAFTA in 1993. The agreement has been renegotiated by the three countries and now is called USMCA, United States-Mexico-Canada Agreement.
