Final answer:
The correct answer is option a) Juan Seguin.
Step-by-step explanation:
The leader of the Spanish-speaking Tejano volunteers who helped defend against General Santa Anna was Juan Seguin. He played a pivotal role during the Texas Revolution, including the defense of the Alamo.
However, regarding the Texas Revolution and the battle in which Texans defeated the army of General Antonio Lopez de Santa Anna, it was the Battle of San Jacinto. This decisive battle led to the capture of Santa Anna and ultimately secured Texas's independence from Mexico.