Answer:
B. It forced Germany to dig defensive trenches along its borders
rather than launching invasions.
Explanation:
World War I is also known as "Trench Warfare" because of the way military operations were carried out. It covered the years 1915 and 1916. It was a consequence of the failure of the lightning war initiated by the Germans in 1914. It meant a change of strategy with respect to the preceding phase and opened the way to the war of stable fronts that immobilized the armies in trench lines which stretched over hundreds of kilometers, from the North Sea to Switzerland.
