Question: Triple-A Plowed Under focused on a period of severe dust storms that was known as what?
Sentence (from "Dust Bowl"): The rapid mechanization of farm equipment, especially small gasoline tractors, and widespread use of the combine harvester contributed to farmers' decisions to convert arid grassland (much of which received no more than 10 inches (250 mm) of precipitation per year) to cultivated cropland.
Relevant evidence: No