Which of the following laws or international agreements limits the free crossing of people over the U. S. and Mexico border? A. the Trade and Border Protection Act
B. the Treaty of Mexico City
C. the North American Free Trade Agreement
D. the Arizona and California Border Patrol Law​

Humans have survived and thrived in mexico city by using technology to create greater access to land. when the spanish conquered the aztec capital, tenochtitlan, in the 16th century, they built mexico city by draining the lakes and filling in the lake water to create more arable land for agriculture. this technique of land reclamation has continued to be fundamental to human civilization in mexico city. 

Physical systems is the answer