A) Slavery was outlawed in Texas, making American settlers angry.
Step-by-step explanation:
In the 1829, slavery became outlawed in Mexican territories, which included Texas. This caused many conflicts between Mexicans and United States settlers.
Many settlers relied on slaves for their income. During this time, agriculture was the prime source of income for many Americans, especially in the Southern states. Settlers would have plantations and farms and needed many people to keep it up, in this case slaves. Slaves would be the ones to tend to the crop and earn money for American settlers, so when this was prohibited it angered many people.
A couple years later, in 1836, Texas gained its independence from Mexico and enabled the use of slavery again.