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
Smooth surface caries refers to 
Select and explain. 
A. Facial and lingual surfaces, B. Occlusal pits and grooves, C. Mesial and distal surfaces, D. Both 1 and 3
D: Both 1 and 3
Answer: D: Both 1 and 3 
Explanation: Smooth surface caries occurs on any of the axial (facial, lingual, mesial, and distal) tooth surfaces but not the occlusal.