The main reason why so many African Americans migrated to cities during World War II was because "<span>D. There were many job opportunities in urban factories."</span>
A flexible expense is something that can be changed at any time. Vacation savings fits the mold of this, as it can be changed. It is not desperately needed, unlike the others.
World War I completely changed the way wars were fought.
Trench warfare, which was the norm just a century ago was seen as an nonviable strategy.
Modern machines such as tanks and airplanes made trench warfare mostly about keeping ground and resulted in stalemates.
Also, it was the first time that modern tanks, planes and machine guns were being used for first time at such a large scale, resulting in an unprecedented level of death and carnage.
Military generals soon realized that time-honored military code of conducts were now obsolete and a completely new form of strategy was now required.
