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
Primary teeth differ from permanent teeth in following aspects 
Select and explain. 
A. Thickness of enamel and dentin, B. Pulp chambers are longer, C. Roots are flaring, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: None