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: Dental
When solid gets wet completely, the contact angle is: 
Select and explain. 
A. 90°, B. 0°, C. 0 — 90°, D. >90°
B: 0°
Answer: B: 0° 
Explanation: None