A whole body dose equivalent to 3000 rem would probably cause death in 4 to 10 days by which of the following mechanisms?

The choice that correctly identifies the mechanism by which a whole body dose equivalent to 3000 rem would probably cause death in 4 to 10 days is related to the gastrointestinal syndrome.

At doses around 3000 rem, the individual experiences massive damage to the cells lining the gastrointestinal tract. This leads to a significant disruption in the ability to absorb nutrients, resulting in dehydration, electrolyte imbalance, and severe infection due to the loss of the protective barrier provided by the gut lining. The rapid onset of these severe symptoms, combined with the extreme nature of the dose, makes gastrointestinal syndrome the primary cause of death within this timeframe.

Other syndromes, such as hematologic syndrome, primarily affect blood cell production and would take longer to manifest to the same lethal degree, while CNS syndrome would typically require even higher doses to manifest its acute effects. Prodromal syndrome refers to initial symptoms that occur shortly after exposure but does not directly cause death. Therefore, the specific and critical mechanism leading to death in this case is the gastrointestinal syndrome.