**Core Concept**
Absence seizures are a type of epilepsy characterized by brief, sudden lapses in consciousness without a loss of postural control. They are often precipitated by hyperventilation and are typically seen in children between the ages of 4 and 10.

**Why the Correct Answer is Right**
The EEG findings in this case are consistent with absence seizures, which are characterized by a generalized 3 Hz spike-and-wave pattern. Hyperventilation can precipitate absence seizures by increasing the concentration of carbon dioxide in the blood, which can affect the excitability of neurons in the brain. This can lead to a sudden loss of consciousness, which may be accompanied by a brief pause in breathing, blinking, or other automatisms. In this case, the girl's symptoms of inattentiveness in class and poor school performance are likely related to the frequency of her absence seizures.

**Why Each Wrong Option is Incorrect**
**Option A:** Myoclonic epilepsy is a type of epilepsy characterized by myoclonic seizures, which are sudden, brief jerks of a muscle or a group of muscles. While myoclonic epilepsy can occur in children, the EEG findings and clinical presentation in this case are not consistent with this diagnosis.

**Option B:** Myoclonus refers to a sudden, brief muscle jerk or spasm. While myoclonus can occur in various conditions, including epilepsy, the EEG findings in this case are not consistent with myoclonus.

**Option D:** Juvenile myoclonic epilepsy is a type of epilepsy that typically presents in adolescence with myoclonic seizures, generalized tonic-clonic seizures, and sometimes absence seizures. While this diagnosis is possible in a 7-year-old girl, the EEG findings and clinical presentation in this case are more consistent with absence seizures.

**Clinical Pearl / High-Yield Fact**
Absence seizures are often precipitated by hyperventilation, which can be used as a diagnostic test in the clinic. This test is based on the fact that hyperventilation can increase the concentration of carbon dioxide in the blood, leading to a sudden loss of consciousness.

**✓ Correct Answer: C. Absence seizure**