单项选择题

Fifty years ago, most people’s daily levels of activity were equivalent to walking three to five miles a day. Today, the (1) person fails to (2) that distance in a week. It’s (3) the ratio of fatness has soared—with serious implications for health.
What we have (4) in convenience from labour-saving devices over the past half- century, we have paid for (5) a sharp decline in physical activity. We use cars, buses or trains to (6) work; our children are (7) to school; elevators and lifts have replaced (8) stairs in shopping centres, offices and apartment blocks. Washing machines, vacuum cleaners, dishwashers and electric mowers all reduce the effort required to (9) a clean and tidy home. Almost one third of adults (10) over ten hours sitting down every day, adding (11) a staggering average of 32 years and four months over a lifetime. (12) surprising, then, that researchers (13) this lifestyle for our weight gain.
Of course, our diets have changed, too, (14) the fact is that we consume fewer calories now than in the 1960s. So what is the (15) The secret is integrated exercise. This (16) going about your normal daily life—but doing it with enthusiasm. It might mean standing to (17) the phone and tapping your feet on the floor as you work. It means never taking the car when you could walk; it means standing on short train and bus (18) , or walking at a pace (19) you feel you might break into a run if you were to go any (20) .

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