Final answer:
The book The History of the Decline and Fall of the Roman Empire by Edward Gibbon is a primary source that provides a firsthand account of the fall of the Roman Empire in the 400s CE.
Step-by-step explanation:
The book The History of the Decline and Fall of the Roman Empire by Edward Gibbon, written in 1776 CE, is a primary source because it provides a firsthand account of the fall of the Roman Empire. Edward Gibbon was a historian, so it was written by an expert and not someone who lived during the fall of the empire. This book is an important source for historians studying the decline and fall of the Roman Empire in the 400s CE.
Learn more about The fall of the Roman Empire