Final answer:
The plague killed over one-third of Europe's population, with the correct answer being option A) One-third. The bubonic plague, including the Black Death, had a massive demographic impact in Europe, eliminating a quarter to half of the population during various outbreaks.
Step-by-step explanation:
In 10 years, the plague had killed over one-third of Europe's population. The correct answer is A) One-third. The bubonic plague, which includes the well-known Black Death, had a catastrophic impact on Europe's population during the 14th century. This outbreak is estimated to have killed approximately one-quarter to half of Europe's population. While the Plague of Justinian affected the population centuries earlier, the later pandemics, such as the Black Death, also had a profound demographic impact, with the population reduction being similarly severe in magnitude.