Concept:The Westminster system is a parliamentary form of government based on the British model.
In Nigeria, this system operated only during the period of civilian parliamentary rule after independence.
Explanation:Nigeria gained independence on October 1, 1960, and immediately adopted the Westminster system of government.
This meant a Prime Minister and Cabinet drawn from parliament, with a ceremonial Governor-General representing the monarch.
The system continued after Nigeria became a republic in 1963, though the ceremonial head changed to a President.
The parliamentary experiment was interrupted and ended by the first military coup on January 15, 1966.
Therefore, the Westminster system in Nigeria lasted exactly from 1960 to 1966.
Answer:Option C: 1960 and 1966.