John d. rockefeller started in the oil industry as a business partner in a refinery. how did he become one of the nation's wealthiest men?
a. he reduced the cost of production by building a huge factory that manufactured equipment for drilling oil.
b. he created a monopoly that controlled most of the production and transportation of refined petroleum.
c. he engineered the purchase of andrew carnegie's steelmaking empire, and then merged the oil and steel industries.
d. he encouraged competition in the oil industry so that technology would remain efficient and cost effective.

Rockefeller is what I personally like to call one of the big 4 entrepreneurs in the 19th century. The other three being Carnegie, Morgan, and Vanderbilt. With the 4 big guys, they all were incredibly vicious. They would do anything and everything to get as much money as possible. Once they got their money, they would be hungry for more. Regardless, I digress. Let's analyze each of the choices:

A. You reduce the cost of production, by producing things (in this case, equipment). That makes no sense at all.
B. That's pretty true. He was known for monopolizing the market, with the other 3 guys.
C. So close. It was actually J.P. Morgan that purchased Carnegie's steel for $750 million dollars. Funny story, he asked Carnegie if he would be willing to sell his steelmaking empire to him, and Carnegie responded that he absolutely would not, for any price. Morgan then pulled out a checkbook, wrote the man a check for $750 million dollars, and handed it to him. Needless to say, Carnegie gave up the steel for that much money (which I think is a couple billion today). Carnegie, after the transaction, asked if Morgan would've been willing to buy his steelmaking empire for $950 million, to which Morgan replied yes, which made Carnegie pretty upset.
D. To make money, you don't want your prospective dollars being put in another place. Encouraging competition detracts money from the company, hurting them economically.

Overall, it's clear that the answer is B.