Concept:The phrase must use a definite article because Abuja is a specific and unique city.
Explanation:When a proper noun names a particular city, the common noun before it takes the article "the."
The correct structure is "the city of Abuja."
The option "A city of Abuja" is indefinite and cannot refer to a single known capital.
The option "City of Abuja" lacks the article and is not grammatically complete in this context.
The option "Abuja of a city" reverses the relationship and makes no logical sense.
Therefore, only one option correctly identifies the specific city.
Answer:B. The city of Abuja.