Read the following passage carefully, Then choose the best answer to each of the questions. The researchers at Lawrence Berkeley National Laboratory in the U.S. studied 7,000 American men to see if exercise prevented the centimeters and kilograms from collecting around their middles. It didn't. Even men who maintained a constant jogging schedule between the ages of 20 and 50 still gained an average of 1.5 kg and added almost 2 cm to their waistlines. The only way to stay slim and trim, say researchers, is to continually increase the amount of exercise with age. To keep his youthful figure, a man who ran 15 km every Saturday in his twenties would have to run a weekly 80 km marathon in his fifties. Sound dispiriting? Even if regular exercise does not keep the spare tire off, it does benefit the heart and lungs. But be sure to take care of your joints especially knees. Wear proper running shoes, run on soft ground when possible and see a doctor if aches and pains persist.