In the 15th century, firearms were used on many medieval battlefields, but only by a small proportion of troops because they were expensive, ineffective, and potentially dangerous to the user; bows and crossbows existed alongside firearms for centuries.

Firearms numbers decreased as the technology became more lethal.

Firearm usage was never a monarch's personal prerogative.

Due to the era’s complete and total lack of anything approaching modern medical knowledge, the majority of Europeans, from nobles and the clergy down to shopkeepers, merchants, and peasants, had no factual idea about the plague’s true cause. Even worse, this lack of understanding extended to the ways in which the disease was spread; even physicians, who lacked knowledge of germs or proper hygiene, could only guess as to how the plague was transferred from person to person. This vast state of confusion only compounded Europe’s fear and panic over the rising sick rate and death toll, as one by one, large population centers found themselves transformed into hotbeds of illness. Desperately seeking any sort of explanation for the disease’s devastation, many people turned to superstitions, extreme religious beliefs, ethnic discrimination, or misguided scientific notions about the natural environment. By far the most popular explanation was that of nameless toxins in the atmosphere – most Europeans believed that unhealthy air was somehow to blame for the plague’s swift spread, although speculation as to the exact makeup of these airborne toxins was varied and essentially baseless. Other individuals blamed earthquakes or volcanic eruptions, which they saw as natural incubators of sickness and disease. Still others turned to religion, speaking out against immorality (such as sexual promiscuity, poor church attendance, and greed) as the instigating factor which had caused God to send down the Black Death as punishment. Due to a pervasive cultural tide of anti-Semitism, many people targeted Jewish citizens as spreaders of the disease as well, but this persecution was more general in nature, and not as particular in its nature as the answer option provided, it was also not as widespread a notion, particular to the plague, as the correct answer option provided.

Milanese armor workshops were so successful that for generations most European armor was heavily influenced by Milanese designs.

Milan's power waxed and waned throughout the middle ages, but it never conquered a large territory and declared a Milanese empire.

Militarily, the Turks were in a period of strength and expansion during this period, conquering Constantinople; they were not threatened by tiny Milan.

The royal houses of Europe desired Milanese armor and armor designed in that style, they did not band together to destroy the source of such advancements.

Most firearms of the period could not pierce plate armor, in fact the final test for all professionally made plate armor was for it to be shot at within close range to prove to a customer that firearms couldn't penetrate. Mounted knights in full plate armor were threatened by firearms, however, because their horses could be shot out from under them.

Junks are sailing ships that were first invented in China during the classical period. Junks came to be popular during the productive years of the Song Dynasty and were used extensively for Chinese voyages in southeast Asia and the Indian Ocean.

Moveable type and printing were both invented first in China. Moveable type allows for the mass production of documents and was first invented in China in the eleventh century, during the Song Dynasty.

Gunpowder was invented in China in the ninth or tenth century. The discovery of gunpowder led to the invention of fireworks and to the invention of firearms. Eventually gunpowder would transform the military and societies of almost everywhere in the world.

Porcelain first emerged in China during the Han Dynasty. During the Tang Dynasty it was an extremely valuable commodity used to trade with Arab traders. By the time of the Ming Dynasty Chinese porcelain was being exported to Europe where it was extremely valuable.

A dhow is a traditional sailing vessel which employs lanteen sails. Dhows were (and are) common trading vessels used by Arab and Indian traders in the Arabian Sea and the Indian Ocean.

Gunpowder was invented in China in the ninth or tenth centuries, during the Song Dynasty, and was first introduced to Europe by the thirteenth century. Most historians believe that gunpowder was introduced to the Europeans by the forces of the Mongol empire at some point in the mid-thirteenth century. Gunpowder, and the introduction of firearm technology, would transform European society.

Muhammad al-Khwarizmi is most notable for his contributions to the development of algebra. He lived in the eighth and ninth centuries, during the Islamic Golden Age of the Abbasid Caliphate. Along with the ancient Greek, Diophantus, he is often credited as “the founder of algebra.”