[单项选择]Getting up earlier than usual or sleeping a couple of hours late can have a significant effect on your mood, according to research published in 1997. When the body’s internal clock, or circadian (生理节奏的) rhythm, gets (67) of accord with your sleep-wake (68) , you can be left (69) out of sorts.
Researchers have long known that moods vary along (70) fluctuations in functions regulated by the body’s (71) 24-hour cycle rhythm, such as body temperature and hormone levels. The (72) of time a person has been awake is also known to (73) mood. To tease apart the two effects, U.S. and U.K. researchers (74) 24 healthy volunteers to live in (75) chambers for approximately three to five weeks and (76) their sleep-wake cycles to (77) a 30-hour or a 28-hour day, (78) than the 24-hour schedule (79) by the rotation of the Earth. Circadian rhythms, which are innate, remained (80) <