How has the region contributed to the interdependence between the United States and Mexico?

The long border between the two countries meant that peace and security in that region are important to the U.S.'s national security and international trade. The U.S. is Mexico's biggest trading partner and Mexico is the U.S.'s third-largest trading partners

i am pretty sure the awsers is d.

i would say your answer is a)

sorry if im wrong