Were the Dust Bowl Survivors refugees or intruders?

The correct answer to this open question is the following.

The Dust Bowl Survivors were refugees, not intruders. In the 1930s, In the middle of the Great Depression, the North American Great Plains suffered from what was known as "the Dust Bowl." The dryness of the land caused large dust storms that affected people, animals, and agriculture. The dust killed cattle and other animals and the lack of water forced people to move from the plains to the Pacific West Coast in order to find new opportunities. That is why they were not intruders, they were trying to survive and feed their families.

the answer is c, all the other options are things they are known for.

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