This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Anatomy
The Hematopoietic syndrome results when acute whole-body radiation exposure is above 
Select and explain. 
A. 50 rad, B. 100 rad, C. 200 rad, D. 400 rad
C: 200 rad
Answer: C: 200 rad 
Explanation: The hematopoietic syndrome results from acute whole-body doses above 200 rads. A prodromal phase consists of nausea and vomiting within the first 12 hrs, with symptoms usually lasting up to 48 hrs. A latent period of 2-3 wks during which patients may feel quite well follows. Although patients are asymptomatic, bone marrow impairment has occurred. The most obvious laboratory finding is lymphocyte depression.