Which caused europe to plunge into the dark ages?

History News Network also mentions that research is placing the Renaissance farther back in the timeline. Effectively, the Dark Ages may not have lacked the intellectual insight that was originally believed. Most of the darkness that occurred in that period happened around the falling Roman empire, as they degraded into feudalism and bloodshed. Some scholars believe the Renaissance can be dated back as far as the reign of the first Holy Roman Emperor, Charlemagne, dated around the ninth century A.D. The term "Dark Ages" is now believed by some to cover a much smaller span of time and geography, with intellectual influence remaining intact in Europe's monasteries well before earlier accepted dates. While the Roman empire's descent was very impacting in that area, its fall did not cause nearly the destruction, ignorance or despair that was once commonly accepted in scholarly circles. It may have only lasted as little as 400 years.

Ifound the exercise on the internet. attached is the list mentioned above.in order for a compound to be considered optically active it can't have any axis or plan of symmetry. the molecule  shouldn't also  be superimposable on its mirror image.with such considerations, the compounds that are optically active are: -third compound on the first image is optically active; -second and third compound from the second image are optically actives.