A group of soldiers, some with visible injuries, walk through a pathway dug into the ground and supported by sandbags. Use the image to answer the question.
The use of the military tactic depicted in the image resulted in which of the following?
A. increased civilian casualties in major European cities
B. a more secure pathway for the movement of refugees through Europe
C. offensive operations against enemies that rarely succeeded
D. the prevention of the spread of contagious diseases among soldiers