Correct answer:
A. The population spread out as people moved to the countryside for safety.
When the city of Rome was under attack and the empire was falling apart, the Romans had to leave. Some native tribes and foreign invaders fought each other for power, but many Roman cities in Britain collapsed when people returned to live in the countryside.
Soldiers who fought in the Crusades brought back knowledge from the Middle East in areas such as medicine, astronomy, and mathematics. The Pope was also a leading figure in politics during this time, and the Crusades helped to unite the different warring nations of Europe while it was being fought. In addition, many kings and monarchs made their claims to fame or brought themselves to ruin due to their Crusading attempts, the most famous example being Richard the Lionheart.
