Which of the following best describes early effects of radiation exposure?

The early effects of radiation exposure are characterized by their dependence on the dose received. This means that the severity and type of early effects—such as radiation sickness, skin burns, or hair loss—are directly correlated with the amount of radiation a person has been exposed to in a short timeframe.

Higher doses of radiation can lead to more severe early effects, and these can appear within hours or days after exposure. This understanding is crucial in radiation protection and safety, where minimizing exposure to harmful doses is a primary goal.

The other options do not accurately describe early effects. For instance, while some effects can be irreversible, it is not a defining feature of early effects, as some may recover depending on the dose and medical intervention. Manifestation of symptoms years after exposure typically relates to late effects rather than early effects, which occur shortly after exposure. Lastly, it is incorrect to state that early effects are always fatal; while high doses can indeed be lethal, not all early effects lead to a fatal outcome, especially at lower doses where recovery is possible.