The group that would have been most supportive of slavery in Texas before the U.S. Civil War is B. Plantation owners. Plantation owners relied on enslaved labor for their agricultural enterprises, particularly in the cotton industry, which was a major economic driver in the southern states, including Texas.
Additionally, D. Texas politicians may also have supported slavery, particularly those aligned with pro-slavery interests, but plantation owners were the most directly involved in and reliant on the institution of slavery for their livelihoods.