Bureaucracy: A system of government or administration where decisions are made by state officials or government employees rather than elected representatives. Bureaucracy refers to government or management carried out by officials and is a one-word substitute for "a government by the officials."
Autocracy: A form of government in which one person has absolute power. This term does not specifically refer to rule by officials.
Monarchy: A form of government where a monarch (king, queen, etc.) holds power, typically inherited. It does not describe government by officials.
Plutocracy: A form of government where power is held by the wealthy. This term is not about government by officials but rather by a specific class of people.
Therefore, "Bureaucracy" is the correct choice as it specifically refers to a government led by officials.