This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
Given device is 
Select and explain. 
A. Vernier calliper, B. Exophthalmometer., C. Dontrix Gauge, D. None of the above
B: Exophthalmometer.
Answer: B: Exophthalmometer. 
Explanation: None