Bicephalous executive is peculiar to system of government.

Step 1: Analyze the question "Bicephalous" means "two-headed." A bicephalous executive is one where executive power is split between two separate heads.

Step 2: Explain the concept In a parliamentary system, the executive has two distinct parts:

• The Head of State is a ceremonial figure, such as a monarch (Queen/King) or a ceremonial President. Examples are the Queen in the UK and the President in Nigeria's First Republic (Dr. Nnamdi Azikiwe).
• The Head of Government is the Prime Minister, who holds the real executive power. Examples are the Prime Minister in the UK and Sir Abubakar Tafawa Balewa in Nigeria's First Republic.

By contrast, a presidential system has a monocephalous (single-headed) executive. The President is both Head of State and Head of Government, as in Nigeria's Second Republic and today.

Step 3: Check the options

• A. Authoritarian: Power is concentrated in one person or group, so it is not two-headed.
• B. Confederal: This describes a loose union of states and says nothing about how the executive is structured.
• C. Federal: This describes the division of powers between central and regional governments, not the structure of the executive. A federation can be presidential (Nigeria today) or parliamentary (Canada).
• D. Parliamentary: It separates Head of State from Head of Government, so the executive is dual.
• E. Presidential: It has a single executive, so it is the opposite of bicephalous.

Step 4: Answer The correct option is D. parliamentary.

Exam tip: Remember the prefix. Bi means two, so bicephalous means two heads, and that is the parliamentary system. Mono means one, so monocephalous means one head, and that is the presidential system.