This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Sleep Disorders, Subject name: Psychiatry
Which waves is predominantly seen in EEG with eyes closed in normal alert adult? 
Select and explain. 
A. Alpha waves, B. Beta waves, C. Theta waves, D. Delta waves
A: Alpha waves
Answer: A: Alpha waves 
Explanation: Ans. A. Alpha wavesBandFrequency (Hz)Location NormallyDelta<4frontally in adults, posteriorly in children; high-amplitude waves* adult slow-wave sleep* in babiesTheta4-7Found in locations not related to task at hand* higher in young children* drowsiness in adults and teensAlpha8-15posterior regions of head, both sides, higher in amplitude on dominant side.* relaxed/reflecting* closing the eyesBeta16-31both sides, symmetrical distribution, most evident frontally; low-amplitude waves* range span: active calm - intense - stressed - mild obsessive* active thinking, focus, high alert, anxiousGamma>32Somatosensory cortex* Displays during cross-modal sensory processing (perception that combines two different senses, such as sound and sight)* Also is shown during short-term memory matching of recognized objects, sounds, or tactile sensations