The word "ignorance" in the given sentence means a lack of knowledge or awareness. The term that is nearest in meaning to "ignorance" among the options is "inexperience."
"Illiteracy" (Option A) refers specifically to a lack of ability to read and write, and it does not capture the broader sense of lacking knowledge or awareness.
"Unfamiliarity" (Option C) is related to not being familiar with something, but it doesn't quite capture the depth of lacking knowledge or awareness as expressed in the sentence.
"Simplicity" (Option D) refers to the quality or condition of being simple, not necessarily to a lack of knowledge or awareness.
Therefore, "inexperience" (Option B) is the most appropriate choice as it aligns with the idea that children behave badly due to a lack of knowledge or experience.