Exercise is good for you, but most people really know very little about how to exercise properly. 【B1】 when you try, you can run into troubles. Many people 【B2】 that when specific muscles are exercised, the fat in the neighboring area is "【B3】 up". Yet the 【B4】 is that exercise bums fat from all over 【B5】. Studies show muscles which are not 【B6】 lose their strength very quickly. To regain it needs 48 to 72 hours and exercise every other day will 【B7】 a normal level of physical strength. To 【B8】 weight you should always" work up a good sweat" when exercising. 【B9】 sweating only 【B10】 body temperature to pr over heating. This is 【B11】 water loss. 【B12】 you replace the liquid, you replace the 【B13】. Walking is the best and easy-to-do exercise. It helps the circulation of blood 【B14】 the body, and has a direct 【B15】 on your overall feeling of health. Experience says that 20 minutes’’ 【B16】. 【B17】 is minimum amount. 【B18】 your breathing doesn’’t return to normal state within minutes after you finish 【B19】, you’’ve done 【B20】.

A．how
B．why
C．nothing but
D．more than