Final answer:
The deepest stage of sleep is experienced during Stage IV, which is characterized by low frequency, high amplitude delta waves and a significant slowdown in heart rate and respiration. Hence the correct answer is option C
Step-by-step explanation:
The deepest stage of sleep is experienced during Stage IV.
During Stage IV sleep, also known as slow-wave sleep, the brain produces low frequency, high amplitude delta waves. It is characterized by a significant slowdown in heart rate and respiration, making it difficult to awaken someone from this stage. Sleep spindles and K-complexes are most often associated with Stage II sleep, which occurs before Stage IV sleep.
Hence the correct answer is option C