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
Radiation caries is caused by irradiation of: 
Select and explain. 
A. Salivary glands, B. Enamel, C. Enamel and dentin, D. Oral mucosa
A: Salivary glands
Answer: A: Salivary glands 
Explanation: None