Final answer:
The two stages of deep sleep are Stage 3 and Stage 4, also known as NREM sleep. They are characterized by slow-wave sleep and low frequency, high amplitude delta waves.
Step-by-step explanation:
The two stages of sleep that are considered deep sleep are Stage 3 and Stage 4, also known as NREM (Non-Rapid Eye Movement) sleep. Stages 1 and 2 are lighter stages of sleep, while Stage 3 and Stage 4 are characterized by slow-wave sleep.
During Stage 3 sleep, low frequency, high amplitude delta waves dominate brain wave activity. This is the stage where an individual's heart rate and respiration slow down significantly. It is also more difficult to wake someone from deep sleep during this stage.
Therefore, option B) Stage 3 and Stage 4 are the two stages of deep sleep.