Answer:
Option: They wanted to seek silver and gold there.
Explanation:
Americans first travel across the Great Plains to get gold and silver in the 1800s. After the Civil War, a vast amount of people from the east began to move in the West in search of gold. The first wave of settlers to the West were miners. The great plains region consists of Texas, Colorado, Kansas, Nebraska, and Oklahoma.
Coal-burning factories and increased automobile usage has caused the greatest increase in "<span>A) air pollution," since in fact coal when burned is one of the worst pollutants. </span>
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1960s<span> in the United States, and eventually spread throughout the Western world and beyond.</span>