**Core Concept**
Petit mal epilepsy, also known as absence epilepsy, is a type of generalized epilepsy characterized by brief, sudden lapses in consciousness. The electroencephalogram (EEG) is a crucial diagnostic tool in identifying this condition.

**Why the Correct Answer is Right**
In petit mal epilepsy, the EEG typically shows a generalized 3 Hz spike-and-wave discharge, which is a distinctive pattern of abnormal electrical activity in the brain. This discharge is thought to be due to the synchronized firing of neurons in the thalamus, a structure in the diencephalon that plays a key role in regulating consciousness. The 3 Hz spike-and-wave discharge is a hallmark of petit mal epilepsy and is often seen in patients with this condition.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the EEG pattern associated with petit mal epilepsy.
**Option B:** This option is incorrect because it is not a characteristic EEG finding in petit mal epilepsy.
**Option C:** This option is incorrect because it is not a specific EEG pattern associated with petit mal epilepsy.

**Clinical Pearl / High-Yield Fact**
When interpreting EEGs in patients with epilepsy, it's essential to recognize the characteristic patterns associated with different types of seizures, such as the 3 Hz spike-and-wave discharge in petit mal epilepsy.

**Correct Answer:** C. 3 Hz spike-and-wave discharge