Question

what is the predominant brain wave activity observed during sleep (nrem)? - delta waves - theta waves - alpha waves - beta waves

Explanation:

During non - rapid eye movement (NREM) sleep, especially in deep sleep stages (stages 3 and 4), delta waves are the predominant brain wave activity. Delta waves have a low frequency (0.5 - 4 Hz) and high amplitude. Theta waves are more prominent in lighter sleep stages (stage 2). Alpha waves are associated with a relaxed, awake state with eyes closed. Beta waves are seen during an active, awake state with eyes open.

Answer:

Delta waves