Based on the graph, what best explains why some Texans became involved in the Civil War? A. The state's use of slaves was starting to increase.
B. The state was preparing to reduce the number of slaves.
C. The state's dependency on slaves was reaching a very high rate.

A. The state's use of slaves was starting to increase.

Explanation:

Based on the graph, it is evident that in the middle of the XIX. century the number of slaves in Texas began to grow sharply. It is evident from the chart that the number of slaves in that state doubled from 1845 until the beginning of the war in 1861 (that is, 1860, as the chart shows). Therefore, it is evident that the main factor in Texas's entry into the war was the effort to maintain slavery in the country.