Exp) Option d is the correct answer.

Option a is incorrect. Federalism is about more and more decentralisation of power. When power is tilted towards the centre then it can be called a Quasi- federal state but not true federal state.

Option b is incorrect. A unitary government is one in which all the powers are vested in the national government. The regional governments, if at all exist, derive their authority from the national government.

Option c is incorrect. Modern democratic governments are classified into parliamentary and presidential on the basis of nature of relations between the executive and the legislative organs of the government. The parliamentary system of government is the one in which the executive is responsible to the legislature for its policies and acts. In such a case, the government may or may not be truly federal.