Which of the following is most susceptible to ionizing radiation?
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.
Mature bone
Small lymphocytes
Nerve cells
Epithelial cells