The correct answers are "fire", "starvation", and "disease".
The First World War was known as a trench war due to the continuous practice of installing trenches along the battlefronts during this conflict.
Trenches were narrow ditches which soldiers used as a temporary shelter while at combat. They located in positions of high proximity to the enemy and were normally used as milestones of an army's advance towards the enemy ground.
However, soldiers located in trenches could be confined to them for long periods of time, spending numerous days without food and also exposed to diseases. Trenches were also easy targets for flamethrowers, as the flames could reach soldiers into places where bullets couldn't.
