Read this excerpt from a passage. In 2010, a research team at the University of Minnesota began a three-year study of later start times at high schools in three states. They compared schools having earlier, more traditional start times with schools starting at times that correspond better to teens' circadian rhythms. Not surprisingly, the results, published in 2014, showed that some positive things happened at the schools with later start times. Students earned higher grades in core subject areas. They performed better on achievement tests. And there were fewer absences and tardy arrivals. The research team reported other benefits associated with a later school start time (which means more sleep for teens). What was the cause associated with the positive effects researchers discovered at the schools? A three-year study of later start times. Students earning higher grades in core subject areas. Continuing using traditional start times. Implementing later start times.