In 235 CE the Roman army was, indeed, on the ropes from Germanic invasions in the North, but the most accurate answer here is the assassination of Severus Alexander by his own troops. The military problems in the North had persisted for sometime, but the real internal strife of the crisis began when the ruler of the Empire was murdered by his own troops as he tried to pacify the Germanic tribes.

By far the most significant military action of the Flavian dynasty was Titus' siege and destruction of Jerusalem in 70 CE. The siege was bloody, and near genocidal in nature, but was considered a major victory for the Empire at the time, and was by far the largest military action of the Dynasty, in terms of man-power and scale.

The Jewish people of Rome held several rebellions against the Empire in the first and second centuries CE. These revolts spurred from various emperor's lack of regard for Jewish customs and practices, and from disagreements on taxation. The other answers are incorrect because these peoples generally assimilated into Roman culture over time.

The northernmost province of the Roman empire was Brittania, what we would call the United Kingdom, so that would be the best choice. The Roman Empire did hold Gaul - France and northern Italy - and various parts of Germany for many years, but they were not the northernmost provinces. Lastly, the Roman Empire never held territory in Denmark or Ireland, so neither of those countries would be good choices.

Tiberius was one of the most accomplished conquerors in the history of the Roman Empire, not to mention the second Emperor of Rome. He led the conquests of large parts of northern Europe (then called Germania) during the reign of Augustus Caesar. During his own subsequent reign, he ordered his adopted-son Germanicus to continue the conquest of northern Europe.

Julius Caesar was the first Roman leader to attempt to invade Britain. He led a limited Roman invasion of the British Isles in 55 and 54 BCE, as part of the Gallic Wars. Several subsequent Roman leaders contributed to the gradual conquest of Britain, which was effectively completed in 43 CE, during the reign of the Emperor Claudius.

The Marcomannic Wars were fought between 167 and 180 CE between the forces of the Roman Empire and several Germanic tribes located in central Europe. The Marcomannic Wars ended in victory for Rome and the extension of Roman influence further into northern and eastern Europe.

The Iceni tribe was one of the most powerful tribes in Britain at the time of the Roman conquest (during the reign of Claudius, in 43 CE). They initially allied with the Roman invaders, but soon rebelled against what they viewed as unfair practices on the part of the Romans. The Iceni rebellion threatened Roman Britain for some time and led to the burning of Londinium (Roman London). The rebellion was eventually crushed and the Iceni were absorbed into wider British-Roman society.

Petra was conquered in 107 CE, during the reign of Emperor Trajan. Trajan is notable for presiding over the Roman Empire during its greatest territorial extent.

Boudicca is remembered by history for leading the Iceni rebellion against the Roman occupation of Britain in 60 CE. The Iceni were Celtic speaking people who lived in Britain before the Roman invasion. Boudicca’s rebellion threatened Roman holdings in Britain for some time before she was eventually defeated.