Final answer:
It is false that Europeans looked forward to guaranteed peace and prosperity at the turn of the century as the continent had not seen a major conflict for 100 years; mounting tensions and aggressive imperialism set the stage for World War I.
Step-by-step explanation:
At the turn of the century, it is false that Europeans could expect peace and prosperity because the continent had not fought a major war for 100 years. Although there was relative peace post the Napoleonic Wars due to the balance of power established, the latter part of the 19th century was marked by a growing tension among European powers, particularly after the unification of Germany.
This tension was exacerbated by aggressive nationalism, colonial expansions, and military buildups, which ultimately led to the outbreak of World War I in 1914. The 'Long Peace' of the 19th century was more about the absence of pan-European wars rather than complete peace, and by 1914 European tensions and alliances made a major conflict increasingly likely.