The first constitution to introduce a presidential system was the

Step 1: Analyze the question The question asks which Nigerian constitution first introduced the presidential system of government, where the President is both Head of State and Head of Government.

Step 2: Recall the concept Nigeria's constitutional history:

• 1960 (Independence) Constitution: Parliamentary system. The Queen was Head of State, represented by the Governor-General, and the Prime Minister headed the government.
• 1963 (Republican) Constitution: Nigeria became a republic, with a ceremonial President (Nnamdi Azikiwe) and an executive Prime Minister (Tafawa Balewa). This was still a parliamentary system.
• 1966: The military took over, and there was no new presidential constitution. Decree No. 1 and the later unitary decrees governed the country.
• 1979 Constitution: Modelled on the American system. It introduced an executive President who was both Head of State and Head of Government, with separation of powers between the executive, legislature and judiciary. Shehu Shagari became President in 1979.
• 1999 Constitution: It retained the presidential system, but it was not the first to introduce it.

Step 3: Solution

• A (1966): Military rule, not a presidential constitution. Wrong.
• B (1963): The President was only ceremonial, within a parliamentary system. Wrong.
• C (1979): First to establish the presidential system. Correct.
• D (1999): Continued the system rather than introducing it. Wrong.

Step 4: Answer The correct option is C. 1979 Constitution.

Exam tip: Remember "79 = Shagari = Presidential." Anything before 1979 (1960 and 1963) was parliamentary. The 1999 Constitution is largely a copy of the 1979 one, so when you see "first," go for 1979.