3. The following passage (paragraph 2) mainly shows that
On June 28, 1914, a Bosnian Serb named Gavrilo Princip shot and killed Archduke Franz Ferdinand, heir presumptive of the Austrian-Hungarian Empire. There had been tensions and smaller conflicts for years, and the assassination set off a chain of war declarations as nations pledged to support their allies or oppose their enemies. Thus began a war of unprecedented scale: a World War. When America entered the Great War, or, as we now call it, World War I, in 1917, they found a new type of warfare. Machine guns, mustard gas, tanks, airplanes, submarines, and other advancements changed the way wars were fought.
A. Gavrilo Princip assassinated Franz Ferdinand
B. the Great War was of an unprecedented scale of destruction
C. the Great War was characterized by massive casualties
D. Gavrilo Princip became one of the most decorated generals of the Great War