24. Whereas many insomniacs believe that they lack sufficient sleep, ----.
A) the chronic inability to either fall asleep or keep sleeping are symptoms of insomnia
B) they should arrange their retiring and rising times so that they spend eight hours in bed
C) evidence shows that they are in fact getting at least as much as they require
D) many people are usually drowsy early in the morning
E) studies have shown that sleeping seven hours a night is associated with the lowest mortality risk