Government by the representatives of the people

Answer: Option B

One word substitute is Democracy.

Diplomacy: the profession, activity, or skill of managing international relations, typically by a country's representatives abroad.
Democracy: a system of government by the whole population or all the eligible members of a state, typically through elected representatives.
Socialism: a political and economic theory of social organization which advocates that the means of production, distribution, and exchange should be owned or regulated by the community as a whole.
Autocracy: a system of government by one person with absolute power.