Question

what challenge did American farmers face in the late 1920s?
A. a drought
B. a seed shortage
C. a lower demand for crops
D. an insect plague

Answer 1

i would go with Drought, because if a big farm is supposed to be watered, there should be a lot of water to do that. 
and if that farmer does not have a lot of it, he is a bad farmer.
He needs water.
But he does not have it, that is called a drought.
Hope that this helps you! =)

Answer 2

C. A lower demand for crops. I read about it. there was no drought.