A、Attending earlier classes often. B、Having a later class schedule. C、Going to sleep much earlier. D、Aiming at a better college.

Here’s some information that might prove useful down the road for high school juniors and seniors: College classes scheduled early in the day correlate with higher gradesor so, says a study from St. Lawrence University. The study, conducted by two psychology professors,followed a sample of 250 students at St. Lawrence and concluded that those who enrolled in earlier classes earned higher grades. Pamela Thacher, a co-author of the study,said she was surprised by the study’s findings,saying she had previously steered students towards later classes so they could get more sleep. But the experiment found a strong link between later class schedules and alcohol use. Those students who chose later classes were likely to binge drink on school nights,and such behavior made for restless,although longer, sleep. Meanwhile, students with an early class were more often discouraged from going out and,as a result,better rested and prepared to engage with the material,reasoned Ms. Thacher. The professors specifically undertook the study to examine whether the start-time patterns of achievement for high school and middle school students held true at the college level. For younger students,research suggests that later class schedules are more helpful to better performance. The factor that makes college different,Ms. Thacher said, is substance abuse. The study also found that women were statistically more likely to earn higher marks than men, though that did not surprise Ms. Thacher, as it was consistent with research at the high school level.
Questions 20 to 22 are based on the passage you have just heard.
20. According to the study from St. Lawrence University, what happens if college students attend earlier classes?
21. What can we learn about Pamela Thacher?
22. What may help middle school students perform better according to the study?