Answer: C. Massive investments in equipment were necessary to make mining profitable
Step-by-step explanation:
After the California Gold Rush of 1829, more and more deposits were discovered in the west of different resources and precious minerals such as gold in Colorado and silver in Nevada.
The prospect of making money from mining was so attractive that thousands of Americans traveled west in the hope of getting rich. Upon getting there however, the prospective miners would quickly discover that mining was no easy task as in the case of gold which was hidden deep in quartz that was underground and so would require massive investment in equipment to get to it.
For this reason, companies came to dominate the mining scene because individuals could rarely afford such expensive machinery.