A Micro-Level Factor That Might Be Part of a Systems

A micro-level factor that might be part of a systems approach to explaining migration patterns between Mexico and the United States is the:

A) U.S. policy that encourages "guest workers" from Mexico to work in American service industries
B) economic condition in Mexico that makes it very difficult for many people to earn an adequate income
C) informal networking among family and friends that provides support for newly arrived immigrants
D) strength of individual-level "push factors" that exceeds that of social-level "pull factors"