The correct answer is B. Justinian gained the throne as his uncle made him co-emperor.
His mother, Vigilantia, was Justin's sister. Justin was part of the imperial guard before being named emperor in the year 518, adopted Justinian and took him with him to Constantinople, ensuring that he received a good education.
Justin was proclaimed new emperor, with significant help from Justinian. During the reign of Justin (518-527), Justinian was the closest confidant to the emperor. Justinian showed great ambition, and it is believed that he functioned as a virtual regent long before Justin appointed him co-emperor on April 1, 527, although there is no evidence to confirm this view. When Justin began to show symptoms of senility at the end of his reign, Justinian became the de facto ruler. Justinian was appointed consul in 521, and later commander-in-chief of the eastern army. After the death of Justin I, on August 1, 527, Justinian would become the sole sovereign of the Empire.
