题目内容：
请根据短文的内容，回答题。College Night Owls Have Lower Grades
College students who are morning people tend to get better grades than those who are night owls ( 晚睡的人) , according to University of North Texas researchers.
They had 824 undergraduate (大学本科生的) students complete a health survey that included questions about sleep habits and daytime functioning, and found that students who are morning people had higher grade point averages (GPAs) than those who are night people.
"The finding that college students who are evening types have lower GPAs is a very important finding, sure to make its way into undergraduate psychology texts in the near future, along with the research showing that memory is improved by sleep," study co-author Daniel J. Taylor said in a prepared statement.
"Further, these results suggest that it might be possible to improve academic performance by using chronotherapy (时间疗法) to help students retrain their biological clock to become more moming types," Taylor said.
The research was expected to be presented Monday at SLEEP, the annual meeting of the Associated Professional Sleep Societies, in Baltimore.
In other findings expected to be heard at the meeting, University of Colorado researchers found a significant association between insomnia (失眠) and a decline in college students' academic performance.
The study included 64 psychology, nursing and medical students, average age 27.4 years, who were divided into two groups--low GPAs and high GPAs.
Among those with low GPAs,69.7 percent had trouble falling asleep,53.1 percent experienced leg kicks or twitches (痉挛) at night,65.6 percent reported waking at night and having trouble falling back to sleep, and 72.7 percent had difficulty concentrating during the day.
"In college students, the complaint of difficulty concentrating during the day continues to have a considerable impact on their ability to succeed in the classroom," study author Dr. James F. Pagel said in a prepared statement. "This study showed that disordered sleep has significant harmful effects on a student's academic performance, including GPAs."
In the first study, students who stay up late ___________. A．had lower GPAs
B．had higher GPAs
C．performed equally well in their studies
D．had little difficulty concentrating during the day
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