Correct Option: C. birth and parentage Detailed Explanation: In Nigeria, citizenship is primarily governed by the 1999 Constitution, which outlines the different ways in which a person can acquire citizenship. The categories of citizenship include citizenship by birth, registration, and naturalization.

1. Citizenship by Birth: This category includes individuals who are born in Nigeria or born to Nigerian parents, regardless of where the birth takes place. According to Section 25 of the Nigerian Constitution, a person is a citizen of Nigeria if at the time of their birth, either of their parents is a citizen of Nigeria. This means that citizenship by birth is a fundamental right that cannot be revoked or declared non-citizen under any circumstance.
2. Citizenship by Parentage: This is closely related to citizenship by birth. It refers to individuals who acquire citizenship through their parents. If a child is born to Nigerian parents, they automatically become a Nigerian citizen, irrespective of where they are born. This principle is rooted in the idea of jus sanguinis (right of blood), which emphasizes the importance of lineage in determining citizenship.
3. Citizenship by Registration: This category applies to individuals who are not citizens by birth but can apply for citizenship through a formal registration process. This often includes people who have lived in Nigeria for a certain period and meet specific criteria. However, citizenship obtained through registration can be revoked under certain circumstances, such as if the individual engages in activities that are deemed contrary to the interests of Nigeria.
4. Citizenship by Naturalization: Similar to registration, naturalization is a process through which a foreign national can become a Nigerian citizen after fulfilling certain requirements, such as residency and good character. Like registration, citizenship by naturalization can also be revoked.

Given this understanding, the categories of citizenship that cannot be declared as non-citizens under any circumstance are those acquired by birth and parentage. These forms of citizenship are inherent and cannot be taken away, as they are based on the individual's lineage and the circumstances of their birth. Why Other Options Are Incorrect:

• Option A: Parentage and Naturalization: This option is incorrect because while citizenship by parentage is indeed a category that cannot be revoked, citizenship by naturalization can be revoked under certain conditions, such as criminal activity or failure to meet residency requirements.
• Option B: Registration and Birth: This option is incorrect because, although citizenship by birth cannot be revoked, citizenship by registration can be revoked. Therefore, this combination does not meet the criteria of being non-revocable.
• Option D: Registration and Naturalization: This option is incorrect for the same reasons as above. Both registration and naturalization are forms of citizenship that can be revoked, making this option invalid.

Revision Summary:

• Citizenship by birth and parentage in Nigeria is irrevocable and cannot be declared non-citizen.
• Citizenship by registration and naturalization can be revoked under certain circumstances.
• The Nigerian Constitution provides clear guidelines on the acquisition of citizenship.
• Understanding the distinctions between these categories is crucial for civic education and awareness of rights.