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
Most "Radiosensitive" Tissue is: 
Select and explain. 
A. Gonads, B. Bone-marrow, C. RBC, D. GIT epithelium
B: Bone-marrow
Answer: B: Bone-marrow 
Explanation: Bone-marrow