Final answer:
One-third to one-half of Europe's population was killed by the bubonic plague after its appearance in 1347. The plague was caused by Yersinia pestis and led to significant socio-economic changes in Europe.
Step-by-step explanation:
The correct answer to the question of how much of Europe's population was killed off by the bubonic plague in the hundred years after it first appeared in 1347 is one-third to one-half. The bubonic plague, known as the Black Death, was one of the most devastating pandemics in human history. It began affecting Europe in 1347 and caused tremendous mortality, reducing the world's population significantly. Although estimates vary, it is widely accepted that Europe experienced a catastrophic loss, with a significant portion of its population succumbing to the disease.
The bubonic plague was caused by the bacterium Yersinia pestis, which is carried by fleas living on black rats. Symptoms included swollen lymph nodes, fever, and, in severe cases, gangrene. The impact of the plague was not just on the human lives lost but also on the socio-economic fabric of Europe, leading to upheavals and a slow recovery of population numbers to pre-plague levels in the following centuries.