Which one of the following in Indian polity is an essential feature that indicates that it is federal in character?

The independence of the judiciary is an essential federal feature because it ensures an impartial arbiter exists to resolve disputes between the Center and States, thereby safeguarding the constitutional division of powers. While option (b) refers to the Rajya Sabha, a bicameral legislature is not a uniquely defining feature of federalism as it can also exist in unitary systems. The core concept being tested is the "Essential Features of Federalism," where an independent judiciary is required to maintain the supremacy of the Constitution in a dual polity.