Step 1: Understanding the relationship.
The man’s father is the brother of his mother’s brother. This means that the man’s father and the man’s maternal uncle are brothers. Hence, the man’s mother’s brother is his maternal uncle.
Step 2: Analyzing the relationship.
Since the man’s father is the brother of the man’s maternal uncle, this makes the man the nephew of his mother’s brother.
Step 3: Conclusion.
The correct answer is (A) Nephew.