<span>The most important advancement that was made by the Maya was B. the 365 day calendar.
This calendar has survived hundreds of years and is still used today. The Maya's were also the ones who developed the concept of the number zero, they predicted the lunar eclipses, and also tracked the cycles of the moon, planets, and stars. The Mayans used this technology they developed to plan for proper harvesting and crop rotations.</span>
When the western Roman empire collapsed in 476 AD, the unifying force for most of Europe was gone. Along with the loss of the government, much of the engineering abilities and "modern amenities" were also lost. The "barbarians" of Europe did not, for the most part, have the abilities or knowledge to build roads, aqueducts or the other marvels of the Roman Empire, which is why the period immediately after Rome's collapse is often referred to as the "Dark Ages".
The only unifying force of any sort left would be Constantine's Roman Catholic church, which did manage to preserve some of the knowledge and vestiges of the empire. As the only thing left really, it became the main power in the European world throughout the Middle Ages, functioning almost as an imperial government until Luther set off the Reformation in 1546.
The Adams–Onís Treaty of 1819, also known as the Transcontinental Treaty, the Florida Purchase Treaty, or the Florida Treaty, was a treaty between the United States and Spain in 1819 that ceded Florida to the U.S.and defined the boundary between the U.S. and New Spain
hope this helps:)
