Let's think about this. If the Great Depression meant there were fewer jobs, which would reasonably occur? A, more jobs were given to immigrants, is wrong, because there weren't enough jobs to go around. Preference would probably be to longtime Americans instead. B, production in factories increased, is wrong. Production must have decreased, because there aren't enough jobs. C, citizens moved to new towns less often, is incorrect--citizens would probably move MORE often in hopes of finding work. But D, Mexican workers were sent back to Mexico, is likely the correct answer: they'd be sent away because there aren't enough jobs, and preference goes to longer American citizens.
Answer: D
