After the fall of the Western Roman Empire, Europe sank into a 700 year period of instability and then began a gradual recovery that led to the Renaissance.
Im pretty sure that two of the answers are B and D
1 and 4 are the best choices since The barbarian attacks killed many romans and the Huns sacked hundreds of cities in the Roman Empire and caused chaos. I also believe 4 is another reason for the decline, since the religion started about 400 years before the fall of the empire and sparked many different believes and divided the Empire through religion.
Answer: Merchants from different places exchange one type of coin to another.
Explanation: Moneychangers were in (virtually) every city's harbor. Traders from foreigns country came to moneychangers to change their money to the local currency (AKA local coin) so that the traders could do buisness in that country