Answer:
A: Drought and D: better-paying jobs led to the mass immigration of Midwesterners to the Southwest.
Step-by-step explanation:
Farmers from the Mid-western bowl states started moving towards California in 1930s. Because of the drought there, especially in Oklahoma and Arkansas, dust storms carried away the top soil and this looked like never ending to the farmers.
These dust storms also created black dark sky even during the day time. So, farmers began to sell their lands and move towards California. When they moved here, they got better jobs and better wages. So, they thought to settle there.