单选题：Exercise Lowers Employers' Health Costs　　Companies can save

　Exercise Lowers Employers' Health Costs　　Companies can save millions in health-care costs simply by encouraging their
employees to exercise a little bit, researchers reported on Friday.
They said obese (肥胖的) employees had higher health-care costs, but lowered
those expenses by exercising just a couple of times a week -- without even losing any　weight.
　　Feifei Wang and colleagues at the University of Michigan studied 23,500 workers at　General Motors.
　　They estimated that getting the most sedentary (关于久坐的) obese workers to
exercise would have saved about $790,000 a year, or about 1.5 percent of health-care　costs for the whole group.
　　Company-wide, the potential savings could reach $7.1 million per year, they
reported in the Joumal of Occupational and Environmental Medicine.
Of the whole group of workers, about 30 percent were of normal weight, 45 percent　were overweight (超重的), and 25 percent were obese. Annual health-care costs　averaged $2,200 for normal weight, $2,400 for the overweight, and $2,700 for obese　employees.
　　But among workers who did no exercise, health-care costs went up by at least $100　a year, and were $3,000 a year for obese employees who were sedentary.
But adding two or more days of light exercise-- at least 20 minutes of exercise or　work hard enough to increase heart rate and breathing---lowered costs by on average　$500 per employee a year, the researchers found.
　　“This indicates that physical activity behavior could reduce at least some of the　harmful effects of excess body fat, and in consequence, help lower the health-care　costs,” Wang and colleagues wrote.How can employees help lower the health-care costs? A．By　taking more res
B．By eating les
C．By exercising a little bi
D．By saving more　mone