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 these cells is most radio-resistant? 
Select and explain. 
A. Early precursor cells of erythroblastic series, B. Muscle cells, C. Fibroblasts, D. Vascular endothelial cells
B: Muscle cells
Answer: B: Muscle cells 
Explanation: None