Answer:
B The war lasted much longer than people expected.
Step-by-step explanation:
The First World War, formerly called the Great War, was a warlike confrontation centered on Europe that began on July 28, 1914 and ended on November 11, 1918, when Germany accepted the conditions of the armistice.
In 1914, Europeans thought that the war would be short. But the generals, who had studied the Napoleonic wars, were wrong in their initial approach to confrontation, based on the massive use of infantry. Responding to the enormous effectiveness of the weapons (rifles, automatic weapons and heavy artillery), the fortifications were reinforced. Cavalry would be useless as a means to break the front.