The correct answer is A) Russia mobilized its Army quickly.
<em>The Schlieffen Plan failed because Russia mobilized its Army quickly.</em>
This was a German plan to attack France and then go for Russia. The attack of France should be through Luxemburg, Holland, and Belgium when Russia started to mobilize its troops. It was designed by Alfred Graf von Schlieffen in 1905. During World War 1, Helmuth von Moltke implemented the plan but with modifications and fewer troops. The idea was to defeat France in six weeks and then going after the Russians. The plan failed due to having fewer troops and a quick Russian troops mobilization that reached the border sooner than expected by the Germans, and the Russians have more troops than the Germans.
Generally we speak of " dark ages " . However, Historians prefer the terms "late antiquity " or "high middle ages" ( it cover the periode from 476 A.D to circa 1000 AD
