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: Radiology
Irregular opaque areas are found on radiographs of lower anterior teeth, the teeth are VITAL the cause may be: 
Select and explain. 
A. Subgingival calculus, B. Cementoma, C. Condensing osteitis, D. Chronic apical periodontitis
A: Subgingival calculus
Answer: A: Subgingival calculus 
Explanation: None