Concept:The first revelation of the Qur'an occurred in a specific month of the Islamic calendar.Explanation:The Qur'an was first revealed to Prophet Muhammad (peace be upon him).This took place in the cave of Hira during the month of Ramadan.The night of revelation is known as Laylat al-Qadr, which falls in Ramadan.Therefore, the revelation of al-Qur'an started in the month of Ramadan.Answer:C. Ramadan