Answer:
Option D, "Sarah is a great little sister, but she really annoys me when she takes toys out of my room," is an appropriate replacement for "She is a great little sister, but she really irritates me when she takes toys out of my room" if Max wants to use less formal language in his journal.
Step-by-step explanation:
Option D is a good choice for a less formal version of the sentence because it uses a more casual verb ("annoys" instead of "irritates") and because it uses Sarah's name instead of just calling her "she." Using someone's name is often more personal and less formal than using a pronoun. The sentence still conveys the same basic meaning as the original, but it does so in a way that feels more like natural speech.