Answer:
B
Step-by-step explanation:
A is incorrect because during this time period, most Western lands were utilized for farming and agriculture, but urban cities.
C is incorrect because droughts weren't very prominent, and even though they were still there, there definitely weren't enough for that to be the main reason for urban immigration.
D is incorrect because most immigrants stayed where the arrived in the US - on the coast (so they didn't settle in rural areas).
Hope this helped!