A、Do a lot of exercises every day. B、Go to sleep early every day. C、Read journals every day. D、Record their mental states. D短文中提

We know that regular fitness is good for the heart and that it can help the body build muscles and maintain healthy weight.(20)It also spurs the release of chemicals—those feel-good chemicals that promote happiness. Researchers from the Penn State University found in their study that the more physically active people reported greater general feelings of excitement and enthusiasm, compared with the less physically active people. The study tracked the daily activities of 190 college-age students,(21)who were asked to record the amount and level of physical activity they got in their free time, the amount and quality of sleep they got each night, and their overall mental states. At the end of each day for eight days, the participants gave their journals to the researchers. "Our results suggest that not only are there chronic benefits of physical activities, but there are discrete benefits as well," one researcher said in the statement. "Doing more exercise than you typically do can give you a burst of pleasant-activated feelings. " Recently, a study came out in the Journal of Business and Psychology showing that(22)bosses who don’t take the time to exercise are more stressed and lash out at their employees, compared with bosses who make time for fitness. Researchers found that the more stressed out the bosses were, the more likely their employees were to say they felt like they were being victimized, the Times of India reported. And, the more the boss broke a sweat, the less abuses were reported on the part of the employee.
20. What is the benefit of regular fitness according to the passage?
21. What should the students in the study do?
22. What happens to those bosses who don’t take exercise?