Concept:Hadith 5 of an-Nawawi warns against introducing new practices into Islam.Explanation:The Hadith narrated by 'Aisha (may Allah be pleased with her) states that the Messenger of Allah (peace be upon him) said: "He who innovates something in this matter of ours that is not of it will have it rejected."This clearly shows that the major teaching focuses on religious innovation, commonly known as bid'ah.The Hadith emphasises that any act added to Islam without authentic basis is unacceptable.Therefore, among the given options, the teaching centres on innovation.Answer:C. innovation