The correct option is A. Supreme Military Council. Detailed Explanation:

1. Historical Context:
2. Nigeria experienced a series of military coups starting in 1966. The first coup occurred in January 1966, leading to the establishment of military rule. The political landscape was drastically altered, and the civilian government was replaced by military leaders.
3. Formation of the Supreme Military Council (SMC):
4. After the first coup, Major General Johnson Aguiyi-Ironsi became the head of state and established the Supreme Military Council as the main governing body. The SMC was responsible for making legislative decisions and governing the country during this period of military rule.
5. Role of the SMC:
6. The SMC functioned as both the executive and legislative authority. It had the power to enact laws, make policies, and govern the country without the need for a parliamentary system, which had been in place during civilian rule. This body was composed of military officers and was the highest decision-making authority in Nigeria until it was dissolved in 1975.
7. Transition to the Armed Forces Ruling Council:
8. In July 1975, a coup led by General Murtala Mohammed replaced General Yakubu Gowon, who had succeeded Aguiyi-Ironsi. The new military regime established the Armed Forces Ruling Council (AFRC), which took over the functions of the SMC. However, this transition occurred after the period in question (1966-1975).

Why the Other Options are Incorrect:

• B. Armed Forces Ruling Council:
• The AFRC was not in existence during the entire period from 1966 to 1975. It was formed later in 1975 after the coup that ousted Gowon. Therefore, it cannot be the correct answer for the main legislative body during the specified timeframe.
• C. Provisional Ruling Council:
• The Provisional Ruling Council (PRC) was established later, during the regime of General Sani Abacha in the 1990s. It was not relevant to the period between 1966 and 1975, making it an incorrect option.
• D. National Security Council:
• The National Security Council (NSC) is typically an advisory body that deals with national security issues and does not function as a legislative body. It was not the main legislative authority in Nigeria during the specified period.

Summary of Key Points:

• The Supreme Military Council was the main legislative body in Nigeria from 1966 to 1975, established after the first military coup.
• The SMC had the authority to enact laws and govern without a parliamentary system.
• The Armed Forces Ruling Council and Provisional Ruling Council were established after 1975 and were not relevant to the period in question.
• The National Security Council serves a different purpose and does not function as a legislative body.

This thorough understanding of the political history of Nigeria during this period is crucial for grasping the evolution of governance in the country.