The answer is A: Constantine recognized the legality of Christianity. This was the biggest change in the Roman Empire to date. Constantine had a change of heart due to a dream he was seen by Jesus- and that is the result he became Christian. In addition, 'the great schism' was a barrier that Constantine and pope were separated (both which they agreed on) due to different ethnicities, languages & culture.
The great schism chart
Constantine's side
East side- middle easterners, Egyptians, turkey
Languages- turkish, Arabica
Pope's side
West side- Rome, Italy
Language- Latin
As a result from McCulloch vs Maryland, two very important consequences aroused. First, the doctrine of the "implied powers" , understanding that the Constitution grants said implied powers to the Congress to implement the express powers. Secondly, that no state action can interfere with valid constitutional exercise of power by the federal government.
The answer is D. The Germans wanted to knock out Russia with its slow moving army then they could focus all of their efforts on France
