What change did the Battle of Waterloo bring in European politics?

Correct answer: Napoleon's rule ended decisively

The direct answer is A: Napoleon’s rule ended decisively. The Battle of Waterloo was fought in 1815, where Napoleon Bonaparte was defeated by the allied army led by the Duke of Wellington, with important Prussian support. After the defeat, Napoleon abdicated and was sent into final exile, ending the Napoleonic era. Option A is correct because Waterloo permanently ended his attempt to regain power. Option B is wrong: the French Revolution began in 1789, about twenty-six years earlier. Option C is wrong because the Russian Revolution belongs mainly to 1917, much later. Option D is wrong because NATO was founded in 1949, not 1815. The useful chain is Waterloo—1815—Napoleon’s final defeat—Congress of Vienna and European reorganisation.