Use the map below of the Roman Empire at its peak to answer the following question:

Map of the Roman Empire at its peak. The highlighted areas include the North African coast, into Egypt, parts of Asia Minor, Mesopotamia, and most of Europe, up to Great Britain.
Public Domain

Which emperor was responsible for extending the boundaries of the Roman Empire as shown on this map?

Augustus (reigned 27 BCE - 14 CE)
Trajan (reigned 98 - 117 CE)
Marcus Aurelius (reigned 161 - 180 CE)
Constantine (reigned 306 - 337 CE)