Concept:The first pledge of Aqbah is an event in early Islamic history that took place before the Hijrah (migration to Madinah).Explanation:During the Hajj season in the 12th year of Prophethood, a group of people from Yathrib (Madinah) met the Prophet Muhammad (peace be upon him) at Aqbah.They accepted Islam and pledged allegiance to him.This event is known as the first pledge of Aqbah.It occurred in 621 C.E., about two years before the migration to Madinah in 622 C.E.Therefore, among the given options, the correct year is 621 C.E.Answer:A. 621 C.E.