Answer:
C. The discovery of oil led to western settlements and farming opportunities.
Step-by-step explanation:
The discovery of oil in Texas happened in the 1860s.
The Western settlements began 20 years before, around 1840s. So we cant' really say that discovery of oil is the one that led into western settlements.
The major incentives that led to the settlements was the availability of cheap lands. Many people who settled in the western part of Norh America saw this as an opportunity to opened up whatever business operation they wanted such as agriculture, mining, slaughterhouse, brothel, etc.