3. Historians would most often use Sinclair's letter to study the
1. Reconstruction Era
2. Suffrage movement
3. Progressive movement
4. Civil rights era

I am going to take a guess and say number 4, Civil rights era.

QwQ

Don't bite me if I'm wrong-

answer: held for the purpose of bringing nazi war criminals to justice, the nuremberg trials were a series of 13 trials carried out in nuremberg, germany, between 1945 and 1949

explanation:

the causes of the dust bowls were severe droughts,   lands became dry and hard, temperature was higher than usual, hot and dry conditions killed crops, high winds. because of those factors, the winds kicked up dry soil and created clouds of dust.