Helle visits her doctor and explains to the doctor that she is having trouble concentrating on her final exams at college and is very short-tempered with her roommates. The doctor asks Helle if she has been sleeping 6-8 hours each night. What may the doctor suspect that Helle is suffering from?
(A) narcolepsy
(B) night terrors
(C) sleep apnea
(D) sleep deprivation
(E) depression