Pandemics, diseases which spread to most populated regions with a high degree of mortality, have been recorded several times in world history, the first being the Plague of Justinian in 541 CE. The Black Death, also known as the Second Pandemic, was one of the most catastrophic events in human history.
The correct answer is letter A. Pre-existing conditions are usually the exclusions of health care programs available in most societies. This is the reason why there are a lot of lawsuits filed against healthcare companies who do not fairly adhere with the interests of their clients/patients.