A 28-year-old woman presents to the ED with her first generalized tonic-clonic seizure. She has no prior medical history. After ensuring airway stability and preventing injury, which of the following is the most appropriate next step in her diagnostic workup?

The correct answer to the question "A 28-year-old woman presents to the ED with her first generalized tonic-clonic seizure. She has no prior medical history. After ensuring airway stability and preventing injury, which of the following is the most appropriate next step in her diagnostic workup?" is Option C: Head CT without contrast.

The other options — A) Lumbar puncture, B) EEG, D) Serum prolactin level — are incorrect for this USMLE Exam Prep question. As explained above: For a first unprovoked seizure in an adult, a head CT without contrast is indicated to rule out acute intracranial pathologies like hemorrhage, tumor, or stroke, which require urgent intervention.