Final answer:
Option a) correctly identifies the similarities between Antonio Cruz and Felix Vargas, providing insight into their friendship and common goals which is central to the narrative's theme.
Step-by-step explanation:
Among the options provided, the correct answer that identifies the three details that tell us how similar Antonio Cruz and Felix Vargas are in the text is: a) Antonio and Felix are both seventeen, both dream of becoming lightweight champions, and they grew up in the same neighborhood.
The reason the author emphasizes these similarities is likely to demonstrate the depth of their friendship and common ground, illustrating a powerful bond that drives the narrative forward and engages the reader in their shared journey toward a common goal.