[单项选择]Making exercise a part of your daily life will do good to your heart. (1) , less than one-fifth of all adults get enough to appreciably improve their health. Exercise has specific heart (2) . When you exercise, you are helping to (3) your blood pressure and cholesterol (4) . Exercise can (5) reduce the blood’s tendency to clot—often a (6) of heart attacks. When major arteries are diseased, (7) even improves the blood supply (8) the heart. You don’t have to become a dedicated runner, jogger, or swimmer to (9) the benefits of exercise. The latest word (10) fitness experts is that small bouts of moderate exercise— (11) for a half hour to an hour, three or four times a week—is (12) you need. Brisk walkers had half the amount of heart disease deaths (13) those who did not walk for aerobic exercise, reports Dr. Steven Blair, head of a landmark study at the Institute for Aerob
A. running
B. racing
C. swimming
D. walking