**Core Concept**
Beta waves in EEG are a type of normal brain activity associated with heightened arousal, attention, and voluntary movements. They are characterized by high-frequency oscillations in the 13-30 Hz frequency range and are typically seen in the cortical regions of the brain.

**Why the Correct Answer is Right**
Beta waves are involved in executive functions such as decision-making, problem-solving, and motor planning. They are also associated with sensory processing and attention. The high-frequency activity of beta waves is thought to be mediated by the activation of NMDA receptors and the subsequent release of neurotransmitters such as dopamine and acetylcholine. These neurotransmitters play a crucial role in modulating the activity of neurons and facilitating the coordination of motor and sensory functions.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because alpha waves (8-12 Hz) are typically associated with relaxation, closed eyes, and decreased cortical activity, whereas beta waves are associated with heightened arousal and attention.
* **Option B:** This option is incorrect because theta waves (4-8 Hz) are typically seen in drowsiness, sleep, and decreased cortical activity, whereas beta waves are associated with heightened arousal and attention.
* **Option C:** This option is incorrect because delta waves (0.5-4 Hz) are typically seen in deep sleep, unconsciousness, and decreased cortical activity, whereas beta waves are associated with heightened arousal and attention.

**Clinical Pearl / High-Yield Fact**
Beta waves can be affected by various neurological and psychiatric conditions, including anxiety disorders, attention deficit hyperactivity disorder (ADHD), and Parkinson's disease. Understanding the normal characteristics of beta waves can help clinicians differentiate between normal and abnormal brain activity.

**Correct Answer:** D.