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
Which of the following is most susceptible to ionizing radiation? 
Select and explain. 
A. Mature bone, B. Small lymphocytes, C. Nerve cells, D. Epithelial cells
B: Small lymphocytes
Answer: B: Small lymphocytes 
Explanation: Tissues that have high sensitivity are lymphoid organs, bone marrow, testes, intestines, mucous membranes. 
Tissues with intermediate sensitivity are ﬁne vasculature, growing cartilage & cartilage,  salivary glands, lungs, kidneys and liver. 
Tissues with low sensitivity include optic lens, mature erythrocytes, muscle cells and neurons.