Constitutional government means

The correct option is A government limited by the terms of the Constitution.

What is Constitutionalism / Constitutional Government?
A constitutional government is defined by the principle of limited government. It refers to a political system where the authority and powers of the government are defined, restricted, and limited by a foundational set of laws or principles known as the Constitution.

Key Aspects of Constitutional Government:

1. Rule of Law: The government operates under rules and laws rather than the arbitrary power or whims of individual leaders.
2. Protection of Fundamental Rights: By placing limits on governmental authority, it ensures that citizens' fundamental rights and freedoms are protected from arbitrary state encroachment.
3. Separation of Powers & Checks and Balances: Power is distributed among different organs of government (legislature, executive, judiciary) to prevent the concentration of absolute authority in any single entity.

Analysis of Options:

• Option A: A constitutional government does not necessarily require a federal structure; unitary systems (like the UK) can also have constitutional governments.
• Options B & C: Whether the Head of State/Government enjoys real or nominal powers depends on whether the system is parliamentary or presidential, not on whether the government is constitutional.
• Option D: This option accurately captures the essence of constitutionalism, which is to limit state authority via the provisions of a constitution.