I do not have your choices of "the following" Here are some reasons I learned: Christianity, empire was too big and became hard to manage, there were many nonromans attacking parts of empire- Goths, the emperors themselves were weak or insane intrigue was rampant.
D. The reason for the fall of the Maya civilization is still unknown. There are many different theories attempting to explain the cause of the Classic Maya collapse and the abandonment of Maya cities in the southern Maya lowlands of Mesoamerica between the 8th and 9th centuries: climate change, drought, deforestation, etc. but although the drought is the leading theory at the moment the truth is yet unknown.
Your last one
the aztec gov was made up...loyal to their kings
The European system of Manorialism is most closely associated with maintaining economic self sufficiency. Manorialism is actually considered a very essential element of the feudal system and society. It is also considered as the organizing principle of most rural economy. I hope this comes to your help.
