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
Anterior openbite & maxillary constriction is caused by: 
Select and explain. 
A. Thumb sucking, B. Nail biting, C. Bruxism, D. Lip biting
A: Thumb sucking
Answer: A: Thumb sucking 
Explanation: None