Answer: B
Step-by-step explanation:
I believe it would be B due to the fact that trench warfare was the most common warfare during world war 1. On the western front, many waves of soldiers would leave their trenches to charge at the other trenches just to be mowed down by heavy machine-gun fire. Many of these charges caused many casualties on little to no ground was gained. The reason why i think it is not C beacuse the Central Powers were on the offensive and and they lost little to no land in europe and actually pushed france and Russia back into their borders. It was only at the end were the central power nations gave up and lost land/