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: Pathology
Which of the following gene is responsible for Fibrous dysplasia: 
Select and explain. 
A. GNAS1, B. GNAS2, C. GNAS3, D. GNAS4.
A: GNAS1
Answer: A: GNAS1 
Explanation: None