Concept: The sacred pilgrimage to Makkah performed by Muslims.Explanation:Hajj is the Islamic pilgrimage to the holy city of Makkah, which every able-bodied Muslim is required to perform at least once in their lifetime.The other options are not the pilgrimage: Ijma is scholarly consensus, Ru'ya means vision or dream, and Salat is the daily prayer.Answer: A. Hajj