Concept:An-Nawawi's Hadith No.9 teaches the importance of moderation in questioning religious matters.Explanation:This hadith presents the Prophet's warning against excessive and unnecessary questioning.It mentions that previous nations were destroyed because of their excessive questioning and their disobedience to their prophets.Therefore, a believer should avoid over-questioning and follow the commands of Allah and His Messenger with humility.Among the given options, this teaching is best captured by moderation in questioning.Answer:A. moderation in questioning