Final answer:
Adolescents typically need at least 8 hours of sleep, according to studies and recommendations by the National Sleep Foundation.
Step-by-step explanation:
The amount of sleep that adolescents need is more than just a number; it’s Critical for their physical, mental, and emotional development. Studies, including those performed by the National Sleep Foundation, have found that on average, adolescents need at least 8 hours of sleep, and often more, such as up to 10 hours for optimal functioning. Considering the data provided, where adolescents average 8.9 hours of sleep, it is clear that option C, which states adolescents need at least 8 hours of sleep, is the correct answer. It is also worth noting that individual needs may vary slightly, and some adolescents might need more than the average amount of sleep.