Answer:
The sentence that is an example of indirect characterization is:
D. I am quick to say thank you and return the favor if someone does something nice for me.
Explanation:
Options A through C use direct characterization. People are being described directly, explicitly, so to speak, through the use of adjectives - "frightened", "childish and immature", "surprised and overjoyed". However, letter D makes use of indirect characterization. Instead of using adjectives, the speaker is describing himself through his actions. When he says he thanks others and returns the favor, we can indirectly infer that he is grateful.
