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
The haematopoetic injury occurs at a dose of: 
Select and explain. 
A. 2-7 Gy, B. 7-15 Gy, C. 40-50 Gy, D. > 50 Gy
A: 2-7 Gy
Answer: A: 2-7 Gy 
Explanation: Acute radiation syndrome:

2–7 Gy – Haematopoietic injury
7–15 Gy – Injury
> 50 Gy – CVS / CNS