Ex1: To be fit and healthy you need to be physically active. Regular physical activities can help protect you (17) ....... serious diseases such as obesity, heart disease, cancer, mental illness, diabetes and arthritis. (18) ....... your bicycle regularly is one of the best ways to reduce your risk of health problems associated with a sedentary lifestyle. (19).......is a healthy low-impact exercise that can be enjoyed by people of all ages, from young children to older adults. It is also fun, cheap and good (20)......the environment. Riding to work or the shops is one of the most time - efficient ways to combine regular exercise with your everyday routine. An estimated one billion people ride (21)......every day - for transport, recreation and sport. 17. A. to B. with C. from D. on 18. A. Riding B. Driving C. Buying D. Selling 19. A. Cycled B. Cycling C. Cycles D. Cycle 20. A. for B. from C. during D. in 21. A. bicycles B. cars C. buses D. boats