The author of “ the high school step team “ reveals karla’s character to readers by describing a. what karla says, does, and thinks b. how jade and other students react to karla c. what karla’s teachers tell her d. why karla is embarrassed in the gym

The answer is: a. what karla says, does, and thinks

The author presents to the reader Karla’s character by showing her thoughts and what she says and does.

For example, there is a part of the story where is thinking about how her cousin has nonverbal reactions “As Karla turned away from Jade and walked down the hall towards math class, she pictured her cousin shrugging her shoulders.”

In other we can also how she prevent herself from learning "It's something like math," she though silently, "but not exactly the same. I have to connect my brain to my body, and make it move or stop at exactly the right moment. The key here is to execute every movement skillfully."  

i believe it is he has been given the drum as a joke.