Concept:Identify the companion from Yathrib who gave the pledge of Islam at the first treaty of Aqabah.
Explanation:The first treaty of Asalah refers to the first pledge at Aqabah, where twelve men from Yathrib accepted Islam.
Al-Bara' b. Ma'rur was one of those twelve men, and he belonged to the Khazraj tribe of Yathrib.
Hence, he is the Yathribite who accepted Islam at this treaty.
Abbas b. Abdul Muttalib was the Prophet's uncle from Makkah, not a Yathribite.
Mus'ab b. Umayr was sent after the treaty to teach Islam in Yathrib.
Therefore, Al-Bara' b. Ma'rur is the correct answer.
Answer:A. Al-Bara' b. Ma'rur