The correct answer is D. Aunt.
C is A’s father’s nephew. This means that C is the son of A’s father’s brother or sister. D is A’s cousin but not the brother of C. This means that D is the son or daughter of A’s father’s other brother or sister. Therefore, D is the nephew or niece of C’s father, which makes D C’s aunt.
Here is a diagram to illustrate the relationships:
A
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B (C’s father)
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C
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D (A’s cousin)
In this diagram, A is the person who is asking the question. B is A’s father. C is A’s father’s nephew. D is A’s cousin.
C is related to D through their shared grandfather. C’s grandfather is A’s father. D’s grandfather is also A’s father. This means that C and D are first cousins once removed.
Aunt is a female relative of a person’s parent, usually the sister of the father or mother. In this case, D is C’s aunt because she is the sister of C’s father.