The answer would be B Regulating commerce
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you can say that Native Americans population was decimated when the Europeans came to colonize the land. Many indigenous people died from diseases.
The correct answer is D) They built windmills and plows.
Because of the dry environment of the West, windmills were built, this helped with the lack of water. Daniel Halladay invented a windmill that pumped water out of a deep well. They also invented dry farming because of the lack of water, when it rained farmers would plow their land so that dust covered the surface. this kept the water underneath the soil.
Because of the weather farmers grew resistant crops such as wheat.
