The correct option is D Aristocracy
'A government by the nobles' is called Option D, Aristocracy. Option A, 'Democracy' is a type of government where citizens have the power of voting ans elect their government. Option B, ' Bureaucracy' is. a system of government where important decisions are taken by the state officials rather than elected representatives. Option C 'Autocracy' is dictatorship . Thus, options A, B and C are incorrect and the correct option is Option D, Aristocracy, for the given phrase.