单项选择题
A．grammar B．damage C．cable D．packagc
A．walking is one of the best exercises B．working up a good sweat is the best way C．walking is better than jogging D．over -exercising is the best way
A．telling readers to exercise for five minutes a day B．pointing out wrong ways in exercising C．giving examples of beneficial exercise D．comparing the results of beneficial exercise and too much exercise