Concept:Ziyarah is not a core act of Hajj; it is a visit to Madinah.Explanation:Ihram is the sacred state and intention for Hajj.Talbiyyah is the proclamation recited during Hajj.Tawaf is the circumambulation of the Ka'bah.These are all essential acts of Hajj performed in Makkah.Ziyarah means visiting the Prophet's Mosque in Madinah, which is not one of the acts of Hajj.Answer:D. ziyarah