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: Pathology
During radiotherapy the Buccal Mucosa exhibits radiation reaction before skin due to - 
Select and explain. 
A. Rapid cellular turn-over in bone, B. Slow cellular turn-over in blood vessel, C. Rapid cellular turn-over in skin, D. Rapid cellular turn-over in mucosa
D: Rapid cellular turn-over in mucosa
Answer: D: Rapid cellular turn-over in mucosa 
Explanation: Rapidly dividing cells are generally more radio sensitive then slowly dividing cells, reflecting radiation induced inhibition of D.N.A. synthesis.