Concept:The underlined word "inquisitive" means having a strong desire to know or learn something.
Explanation:In the sentence, "inquisitive" describes someone who is eager to ask questions and find out new information.
We compare it with the options provided.
Option A "naughty" means disobedient and badly behaved, which is unrelated.
Option B "playful" means full of fun and enjoyment, which does not convey an eagerness to learn.
Option C "curious" means eager to know or learn something, which exactly matches "inquisitive."
Option D "troublesome" means causing worry or difficulty, which is not the intended meaning.
Therefore, the word nearest in meaning to "inquisitive" is "curious."
Answer:Option C. curious