Which of the following describes a unitary system of government?
A. a federal arrangement of central government and
states
B. the United States under the Articles of
Confederation c. a country in which the central government holds
all the power
D. independent legislatures in several provinces

the answer is

world war i began in 1914, after the assassination of archduke franz ferdinand, and lasted until 1918. during the conflict, germany, austria-hungary, bulgaria and the ottoman empire (the central powers) fought against great britain, france, russia, italy, romania, japan and the united states (the allied powers). to new military technologies and the horrors of trench warfare, world war i saw unprecedented levels of carnage and destruction. by the time the war was over and the allied powers claimed victory, more than 16 million people—soldiers and civilians alike—were dead.

explanation:

they became hereditary because there weren't many jobs for people in lower classes