Which syndrome associated with Acute Radiation Syndrome (ARS) includes symptoms like fever and lethargy?

The correct identification of hematopoietic syndrome in the context of Acute Radiation Syndrome (ARS) is based on its characteristic symptoms and the biological effects of radiation exposure on the bone marrow and blood system. Hematopoietic syndrome occurs when radiation exposure leads to a significant reduction in the number of blood cells, which in turn causes a wide range of systemic effects. Symptoms like fever and lethargy are indicative of this syndrome, as they often arise from the body’s response to infection and anemia, conditions frequently associated with the destruction of blood cells and the immune system's compromise.

The fever can be a response to infections that occur due to neutropenia, where the number of neutrophils is reduced, compromising the body’s ability to fight infections. Lethargy might arise from anemia due to reduced red blood cell counts and the consequent decreased oxygen delivery to tissues.

Other syndromes associated with ARS present with different symptoms; for instance, gastrointestinal syndrome relates primarily to damage of the intestinal lining, causing severe nausea, vomiting, and diarrhea. Cerebrovascular syndrome is associated with higher doses of radiation causing neurological symptoms like confusion and seizures, while neurological syndrome involves severe central nervous system symptoms due to high-level exposures.