All of the options you provided can be considered effects of mining in the West, but if you are looking for the most prominent and direct effects, the following two stand out:
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The population increased greatly as people came hoping to get rich. - This is a fundamental outcome of the mining boom, particularly during events like the Gold Rush, which attracted a massive influx of people seeking fortune.
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Large permanent cities developed around the mining camps. - As mining camps grew, many evolved into permanent settlements and cities, leading to the establishment of towns and infrastructure in the region.
While the other options you mentioned also have some validity, they are more indirect or less prominent compared to the population increase and the development of permanent cities.