Final answer:
The new technology of machine guns in World War I helped lead to the system of trench warfare.
Step-by-step explanation:
In World War I, the new technology of machine guns played a significant role in leading to the system of trench warfare (A). The introduction of machine guns, along with other weapons like mines and modern rifles, made it more effective to defend a position rather than attempt to charge and take the enemy's position. This shift in strategy favored defensive tactics and led to the development of elaborate trench systems on both sides of the conflict.