Remember, INDIRECT characterization is where the author tells you details about the character, and you have to use this information to infer the character's personality. DIRECT characterization is the opposite: where the author specifically tells and describes to you a person's character traits.
Let's look at option A: "Jeff was a kind boy who was always willing to help anyone in need." Already, we know this is NOT indirect characterization: it is DIRECT characterization. Why? The sentence calls Jeff "kind," which is a character trait. We don't need to infer that.
What about B? "Mariana was a chatterbox and could talk for hours about any subject." Here's the key word: "chatterbox." This is more direct characterization.
Let's look at C: "Juan pretended to be sick so that she would not have to go to school." Do you see any direct descriptions of Juan's personality? No! From this, we could infer that Juan is willing to break the rules. Perhaps she's having a hard time at school.
Just to check, look at D. "Iamar was jealous of his older brother Omar, who was a skilled soccer player." This one is a little trickier, because this passage has two characters: Iamar and Omar. But what do we know about Omar? He is "skilled" at soccer. Again, we have direct characterization here, so D isn't correct.
Answer: C