Final answer:
The assassination of Caesar led to the establishment of the Second Triumvirate, formed by Octavian, Mark Antony, and Lepidus to avenge his death and bring stability back to Rome.
Step-by-step explanation:
The event that led to the establishment of the Second Triumvirate was a. the assassination of Caesar. This pivotal moment in Roman history occurred on March 15, 44 BC, which is famously known as the Ides of March.
Following Caesar's assassination, three of his supporters—Octavian (later Augustus), Mark Antony, and Lepidus—formed the Second Triumvirate, with the intent to avenge his death and stabilize the Roman Republic. The triumvirate ultimately led to the end of the republic and the beginning of the Roman Empire.