How did advances in military technology contribute to the stalemate that developed in Europe during world war I?
A. Countries rarely attacked one another's land, as most fighting took place on advanced naval vessels.
B. Few leaders risked large-scaled attacks, as tanks and aircraft were too valuable to risk in battle.
C. Armies were unable to capture much territory, as it was defended by troops with machine guns.
D. Soldiers remained healthy in trenches, as cars and trains rapidly supplied them with food and medicine.