Step 1: Understanding unitary system.
In a unitary system of government, all powers are centralized in a single authority (the central government). States or provinces, if they exist, function only as administrative units without independent powers.
Step 2: Analyzing the options.
(A) India: Federal system with division of powers between Centre and States.
(B) England: Correct — the UK follows a unitary system where Parliament is supreme.
(C) United States of America: Federal system with strong states.
(D) Australia: Federal structure.
Step 3: Conclusion.
Thus, the country with a unitary system here is England.