Concept:The first Mu'adhdhin (caller to prayer) in Islam was a companion chosen by Prophet Muhammad (peace be upon him).Explanation:The term "Mu'adhdhin" refers to the person who makes the Adhan (call to prayer).Bilal ibn Rabah, an Ethiopian companion, was chosen as the first Mu'adhdhin in Islamic history.He was selected because of his beautiful and powerful voice, as well as his deep faith and devotion.Thus, among the given options, Bilal is the correct choice.Answer:A. Bilal