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
Magnesium deficiency has been reported as an etiological cause for: 
Select and explain. 
A. Bruxism., B. Nail biting., C. Thumb sucking., D. All of the above.
A: Bruxism.
Answer: A: Bruxism. 
Explanation: None