The best description of the conditions faced by soldiers during the Civil War is: Poor conditions were made worse in that most soldiers were young men under the age of 21.
This statement reflects the reality that many soldiers were indeed young and inexperienced, facing harsh conditions in terms of supply shortages, poor sanitation, inadequate medical care, and challenging living conditions. While improved military technology led to higher casualty rates, the notion that most soldiers died instantly is an oversimplification, as many suffered from wounds and infections over time. Additionally, the other statements do not accurately capture the overall experiences of Civil War soldiers.