context: Biblical study experts give different names to each of the three sections of this book. Chapters 1-39 are called Proto-Isaiah, chapters 40-55 are called Deutero-Isaiah, and chapters 56-66 are called Trito-Isaiah. They also suspect that each part was written by a different writer. However, this conjecture is now considered incorrect again with the discovery of the "Great Isaiah Scrolls" among the Dead Sea Scrolls. The scroll contains the entire book of Isaiah in Hebrew in full and is thought to have been written in 125 BC. Because this is a complete copy and no partial copy was found, experts believe that the original book was written complete long before, namely before the exile, and copied during the exile until his return to the land of Israel again. [2]
question: When was the Book of Isaiah written?
answers.text: 125 BC