How did large mining companies succeed? a. they set up towns to sell supplies to individuals looking for gold. b. they used machines to dig deeply for gold. c. they paid for individual miners to come west to look for gold. d. they set up operations where individuals had not found gold.

B. They used machines to dig deeply for gold.

Explanation:

After the first rush to the western gold mining towns, large mining companies took over mining operations.  

They replaced individual miners so that they could make more money.

Individual miners couldn't compete with hydraulic mining and hard-rock mining.