Search the subreddit for specific page numbers. For example, "Nihongo Challenge page 42 answer key doubt." The community often provides explanations that the bare answer key cannot provide (e.g., cultural context, grammar nuances).
Nihongo Challenge Kanji N4-N5 Guide on Scribd . Nihongo Challenge Kanji N5 Answer Key
Lesson: Never forget the trailing hiragana. The kanji alone is a noun; plus okurigana makes it a verb. Search the subreddit for specific page numbers