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: Medicine
Siblings of the diagnosed patient with Wilson disease will be having what risk of Wilson disease? 
Select and explain. 
A. 25%, B. 50%, C. 75%, D. 100%
A: 25%
Answer: A: 25% 
Explanation: The frequency of Wilson's disease in most populations is about 1 in 30,000. Siblings of a diagnosed patient have a 1 in 4 risk of Wilson's disease. Reference: Harrisons Principles of Internal Medicine, 18th Edition, Page 3188