The author of the high school step team reveals Carlos’s character to readers by describing

What Carla says does and thinks
How Jaden other students react to Carla
Carla’s teachers tell her
Why Carla is embarrassed in the gym

The correct answer would be:

What Carla says, does, and thinks.

By describing Carla's actions, words, and thoughts, the author reveals Carlos's character to the readers.