Final answer:
The significant population decline in the 1350s was caused by The Black Plague (C), also known as the bubonic plague.
Step-by-step explanation:
The significant population decline in the 1350s was caused by The Black Plague (C), also known as the bubonic plague. This deadly disease was carried by fleas on rats and spread rapidly throughout Europe, causing the death of millions of people. The Black Plague had devastating effects on society, leading to the decline of cities, economic disruption, and a shift in power dynamics.
Learn more about Effects of The Black Plague in the 1350s