(A) a stalemate
(B) more people were killed
(C) ** the war was sped up
(D) soldiers were exposed to horrible conditions
EXPLANATIONS BELOW
Concept note-1: -During World War I, trench warfare was a defensive military tactic used extensively by both sides, allowing soldiers some protection from enemy fire but also hindering troops from readily advancing and thus prolonging the war.
Concept note-2: -As they were often effectively trapped in the trenches for long periods of time, under nearly constant bombardment, many soldiers suffered from “shell shock, ” the debilitating mental illness known today as post-traumatic stress disorder (PTSD).