Answer:
The change in breastplates and helmets contribute to decline of the Roman Empire by weakening the the military. It weaken them because the removal of it promote laziness and negligence of training and the such. It also removes the protection against ranged weapons which caused many casualties.
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The answer to your question is D.
Because during the world war a lot of workers were not happy the low pay.
If by Christian Church you mean Catholic Church(as their was and is the Eastern Orthodox, which historically didn't get along well with Catholics) then the Reformation.