2. By 476 AD, Christianity has spread to most of the Roman Empire, and, in some cases, past those borders.
Explanation:
By the year of 476 AD, the Christianity has become the primary religion in the Roman Empire, and taken in consideration its size and population, it became the dominant religion in Europe as well. There were several reasons as to why the Christianity spread out and became dominant so quickly.
One reason is that the people were desperate in this period, and they needed a savior, someone that will give them hope, and Jesus seemed to be the perfect match. Also, the Roman aristocracy accepted it, so in order to control the empire better they made it the official religion. Soon, the Christianity spread in almost all of the Roman Empire, except parts of North Africa, and in some areas outside the empire.
3. Most Christians lived along the coasts of the Roman Empire.
Explanation:
In the year of 325 AD, the majority of the Christians lived along the coastlines of the Roman Empire. This was due to the fact that the coastal areas had much more contact with the other areas of the empire, so naturally, through trade and exchange of ideas, the new religion got its way to the trading centers.
Some people started to accept it, while some didn't, as it was a big change for lot of people. Also, the areas in the interior of the empire, having less contact with the areas further away, lacked Christian populations.
4. Mountains made this region difficult to access.
Explanation:
The Roman Empire was the most powerful empire in Europe for quite some time, and by the year of 107 CE, it managed to occupy vast territories, including Gaul and the Iberian Peninsula. What's interesting is that the area between these two was actually not conquered by Rome in this period of time, but it took longer and much more effort to do so.
The reason for this was simple, the geography of this area. It is an area dominated by high mountains with steep slopes and dense forests. The people that lived there had excellent natural protection and good strategic location for defense. Also, the Roman army was not designed for such terrain, which just made everything much slower and much more difficult.