Final answer:
Marcus Aurelius was succeeded by his son Commodus, whose reign was notorious for his indulgence in decadence and his participation in gladiatorial battles, which led to questions about his legitimacy and contrasted sharply with his father's philosophically minded and efficient rule. The correct option is b.
Step-by-step explanation:
Marcus Aurelius, the last of the Five Good Emperors and a practitioner of Stoicism, was succeeded by his son Commodus after his death.
Commodus's reign, commencing in 177 CE as co-emperor and continuing until his assassination in 192 CE, marked a significant departure from his father's prudent and philosophical approach to governance.
Commodus was known for his debauchery, neglect of state affairs, and unprecedented behavior as an emperor by participating in gladiatorial combat, which was seen as madness and below the dignity of his station.
The appointment of Commodus as Marcus Aurelius's successor was not only a result of his being the natural-born son who survived into adulthood, but it also reflected a break from the tradition of choosing a competent heir based on merit.
These rumors were exacerbated by the stark contrast in leadership style between father and son, which led to speculation about Commodus's parentage and his mother Faustina's fidelity. The correct option is b.