Which domestic shift most affected the demographic makeup of northern US cities in the early 1900s?

A. migration of African Americans from southern farms to northern factories
B. influx of illegal immigrants from Mexico and Central America
C. discovery of large coal deposits in some midwestern states
D.US acquisition of Puerto Rico and the Philippines after the Spanish-American War
E. US victory over Mexico in the Mexican-American War

Question

Which domestic shift most affected the demographic makeup of northern US cities in the early 1900s?

A. migration of African Americans from southern farms to northern factories 
B. influx of illegal immigrants from Mexico and Central America
 C. discovery of large coal deposits in some midwestern states
 D.US acquisition of Puerto Rico and the Philippines after the Spanish-American War
 E. US victory over Mexico in the Mexican-American War