Answer: B. Two
Explanation:
During the first stage, your body starts relaxing and falling into sleep. This is the lightest stage of sleep. You can wake easily during this stage, and are not "fully" asleep.
During the second stage, your body deepens into it's sleep, your heart rate decreases, your body temperature decreases, and more. <em>This is the stage that "represents the beginning of actual sleep" which is the answer to your question.</em>
During the third stage, your body is in a deeper state of sleep. Your muscles relax further, your breathing rate slows, and more.
During the fourth stage, your heart rate and body temperature rise again. Your brain is a bit more active, and your muscles start to "wake up" slowly again.
<em> Read more about </em><em>NREM sleep</em><em> here:</em>
<em>brainly.com/question/14410334</em>
