Final answer:
The child's symptoms and behavior indicate an absence seizure, which is characterized by brief episodes of loss of consciousness and lack of response to stimuli.
Step-by-step explanation:
The brief episode of eyelid fluttering and slight loss of muscle tone, followed by inattentiveness for 15 to 20 seconds, suggests a type of seizure called an absence seizure.
In absence seizures, also known as petit mal seizures, the person experiences a brief loss of consciousness, characterized by staring into space and an absence of response to stimuli.
During an absence seizure, the person may exhibit subtle signs such as fluttering eyelids, slight muscle weakness, or slumping in their chair, and will typically return to normal after the seizure.