Explanation: Gross domestic product measures overall economic output, directly quantifying growth in the U.S. and contraction in the Soviet Union and Britain during WWII, supporting the passage's claims about civilian economy performance. Territory controlled indicates military success but not economic health. Military size reflects mobilization and resource allocation but not civilian consumption or economic expansion. Birth rates are demographic indicators, influenced by economy but not direct evidence of output or consumption changes.

Explanation: The collapse of the Western Roman Empire in 476 CE resulted in the breakdown of centralized governance, leading to the rise of numerous barbarian kingdoms that divided the territory politically. Economic activities declined as long-distance trade routes deteriorated, urban centers shrank, and agricultural production became more localized and less efficient. The Islamic world did not emerge until the 7th century, so economic flourishing through trade with it was impossible in the immediate aftermath. Unification under Christianity was a gradual process spanning centuries, not quick or driven by state sponsorship in the chaotic post-Roman period. Cultural and intellectual development suffered, with literacy rates dropping and much classical knowledge lost or preserved only in isolated monastic communities, contrary to a period of rich development.

Explanation: In 1958, Mao Zedong launched a campaign to collectivize agriculture into people's communes and boost industrial production, intending to accelerate China's development but resulting in catastrophic famine and millions of deaths. The Great Proletarian Cultural Revolution was a later movement from 1966 to 1976 aimed at purging capitalist elements and consolidating Mao's power through mass mobilization. The National Liberation Front was a political organization in South Vietnam during the Vietnam War, unrelated to Chinese policies. The Down to the Countryside Movement was a policy during the Cultural Revolution sending urban youth to rural areas for re-education and labor.

Explanation: The Triple Entente was formed through a series of agreements: the Franco-Russian Alliance of 1894, the Entente Cordiale between France and Britain in 1904, and the Anglo-Russian Entente in 1907, creating a counterbalance to the Triple Alliance. The Ottoman Empire joined the Central Powers in WWI. Austria-Hungary was a member of the Triple Alliance with Germany and Italy. Italy was part of the Triple Alliance but did not join the Central Powers at the start of the war and eventually sided with the Entente in 1915.

Explanation: The 1918 influenza pandemic, also known as the Spanish Flu, spread rapidly due to wartime conditions, troop movements, and demobilization, infecting about one-third of the world's population and causing massive mortality rates far exceeding those of the war itself. Typhus epidemics occurred in some regions like Eastern Europe but did not cause global deaths on this scale. Malaria was endemic in tropical areas but not responsible for a post-war pandemic. Tuberculosis was a chronic disease with high mortality but its deaths were ongoing, not concentrated in a single epidemic event following the war.