How Many Hours of Sleep Do Older Adolescents Require for Optimal

How many hours of sleep do older adolescents require for optimal functioning?

A) 9 hours per night; they need to go to bed later and to sleep later in the morning.
B) 8 hours per night; they need to go to bed earlier and to get up earlier in the morning.
C) 7 hours per night; they need to go to bed later and to sleep later in the morning.
D) 6 hours per night; they need to go to bed earlier and to get up earlier in the morning.