Final answer:
The primary source for the Gospel of Mark is believed to be oral traditions and possibly early Christian writings, shaped by the teachings of Jesus's apostles, particularly Peter.
Step-by-step explanation:
Mark's primary source for his Gospel account is widely debated among scholars. However, the prevailing theory is that Mark may have relied on a variety of sources including oral traditions, testimonies of witnesses, and other early Christian writings.
The Gospel of Mark, being the earliest of the four canonical gospels, is thought to have influenced the other Synoptic Gospels—Matthew and Luke. Important to note is that while Mark was not one of the twelve disciples, he may have been a follower of Peter, one of Jesus's closest apostles, providing him access to firsthand accounts. The Gospels were transmitted orally for decades and were only written down in their definitive versions around 90 CE, approximately sixty years after Jesus's death. Therefore, it is believed that the oral traditions and teachings of the apostles played a significant role in shaping Mark's account of Jesus's life.