未知题型 Which of the following interpretations of the biologists' theory about melatonin is INCORRECT?A.The production of melatonin in our bodies varies at different times.B.Melatonin is more likely to cause sleepiness in our bodies.C.The reduction of melatonin will cause wakefulness in our bodies.D.The amount of melatonin remains constant in our bodies.

单项选择题 紧急呼叫(SOS)需要进行附着以后才能发起的网络服务（ ）

未知题型 Which of the following can best sum up the author's overall reaction to her adult son's positive response to spring cleaning?A.Surprised and skeptical.B.Elated and hesitant.C.Relieved and optimistiC.D.Optimistic and hesitant.