<prompt> During which of the following sleep stages shows sleep spindles in ECG?Stage 1Stage 2Stage 3Stage 4  <response>: Ans. B. Stage 2Stage 1 sleeppresence of theta waves 4-HzStage 2 sleepSleep spindles appears as sinusoidal waves occurring at a frequency of 12-14 Hz. Presence of sleep spindles and K complexes. K complexes are occasional high voltage biphasic waves.stage 3A high-amplitude delta rhythm 0.5-4 Hz are seen.Stage 4presence of slow waves. 