**Core Concept:** A febrile seizure is a type of seizure that occurs in a child during a fever, typically caused by an infection. These seizures are classified as either simple or complex, depending on their duration. A simple febrile seizure lasts for <15 minutes and typically involves one limb. A complex febrile seizure is longer than 15 minutes and may involve multiple body areas. **Why the Correct Answer is Right:** A complex febrile seizure lasts longer than 15 minutes, making it different from a simple febrile seizure. This prolonged duration increases the complexity of the seizure and warrants a different classification. **Why Each Wrong Option is Incorrect:** A. A febrile seizure lasting 15 minutes would be considered a complex febrile seizure, not "simple." So, options A, B, and C are incorrect because they suggest durations shorter than 15 minutes. B. Duration is the key factor differentiating simple from complex febrile seizures. Other characteristics like the seizure's involvement of multiple body areas are not as critical as duration. C. Similar to option A, a febrile seizure lasting 15 minutes would still be classified as complex. D. A febrile seizure lasting 30 minutes is longer than the required duration for a complex febrile seizure, making it incorrect. **Clinical Pearl:** The differentiation between simple and complex febrile seizures is crucial, as complex febrile seizures increase the risk of future epilepsy development, requiring closer monitoring and potentially different treatment approaches. **Correct Answer:** .