How were the oil and steel industries in the late 1800s established and what were the pros and cons of the creation of these big businesses?

The correct answer to this open question is the following.

The oil and steel industries in the late 1800s were established due to the wit of prominent wealthy men John D. Rockefeller, who owned the Standard Oil Company, and Andrew Carnegie, owner of the Steel company. The pros and cons of the creation of these big businesses were that although they created many jobs, these companies grew so much, bought most of the competitors and were known to be monopolies in America. Both companies practically controlled the oil and steel industry, respectively. And the jobs they created were low paid jobs under harsh conditions and laborers had to work for long hours.  

d.he wanted to send diplomats to communist countries.

a because i tried to vote with just my college id and the answer was no