**Core Concept**
Buerger waves, also known as alpha waves, are slow-wave oscillations observed in the EEG during relaxed wakefulness with closed eyes. These waves are primarily associated with the idling state of the brain and are a key feature of normal brain activity in the absence of cognitive engagement.

**Why the Correct Answer is Right**
Alpha waves (13–30 Hz) are most prominent in the occipital lobes when a person is relaxed and eyes are closed. They are typically seen in the range of 10–16 Hz in adults, with the classic "alpha rhythm" falling between 13 and 30 Hz. This frequency range is distinct from other EEG waves like delta (0–4 Hz), theta (4–7 Hz), and beta (13–30 Hz), though beta overlaps with the upper end of alpha. The term "Buerger waves" refers to this alpha wave pattern, and their frequency is firmly established in neurophysiological literature.

**Why Each Wrong Option is Incorrect**
Option A: 0–4 Hz is the delta wave range, associated with deep sleep or unconsciousness, not alpha waves.
Option B: 7–4 Hz is not a valid range (4–7 Hz is theta), which occurs during drowsiness or light sleep, not relaxed wakefulness.
Option D: 13–30 Hz includes both alpha and beta waves, but the *classic* alpha wave range is specifically 10–13 Hz, not extending to 30 Hz. However, the broader range 13–30 Hz is accepted in many textbooks as the alpha wave band, especially when including beta activity. Still, option C is more precisely aligned with standard definitions.

**Clinical Pearl / High-Yield Fact**
Alpha waves disappear when a person opens their eyes or engages in mental activity. Their presence indicates a relaxed, alert state and is used clinically to assess brain function in EEG studies.

✓ Correct Answer: C. 13-Aug