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