Final Answer:
The interpretation of the man's exclamation is (A) is a nice-looking animal.
Step-by-step explanation:
The lines indicate that the man's eyes light up upon seeing Buck, and he exclaims that Buck is a "bully dog." In this context, "bully" is likely used in its older sense, meaning splendid or excellent, rather than suggesting aggression. The phrase "His eyes lit upon Buck" and the positive exclamation suggest that the man is expressing admiration for Buck's appearance, making option (A) - "is a nice-looking animal" - the most fitting interpretation.
The use of the term "bully dog" in a positive sense aligns with the admiration and positive reaction of the man upon seeing Buck. This characterization implies that the man sees Buck as an impressive and visually appealing dog rather than indicating any negative traits.
In conclusion, the man's exclamation conveys a positive impression of Buck, emphasizing his admiration for the dog's appearance. Therefore, option (A) - "is a nice-looking animal" - accurately captures the intended meaning of the lines.