Concept:The legal document that granted Nigeria's independence was an Act of the British Parliament.
Explanation:Nigeria was a British colony, so its independence had to be legally granted by the Parliament of the United Kingdom.
The Nigerian Independence Act of 1960 was passed by the British Parliament for this purpose.
This Act conferred full sovereignty on Nigeria with effect from 1 October 1960.
The Lancaster House Agreement relates to Zimbabwe's independence, not Nigeria's.
The Atlantic Charter was merely a wartime statement of principles and did not grant independence to any colony.
The United Nations Declaration on Decolonization was a general policy declaration, not the specific legal instrument that made Nigeria independent.
Therefore, the Nigerian Independence Act remains the correct legal document that granted Nigeria its independence.
Answer:C. The Nigerian Independence Act