题目内容：
根据以下资料，回答题。
People need to be active to be healthy．Our modem lifestyle and all the conveniences we've become used to have made us sitting much of the time - and that's dangerous for our health．Sitting around in front of the TV or the computer, riding in the car for even a short trip to the store and using elevators instead of stairs, all contribute to our inactivity．Physical inactivity is as dangerous to our health as smoking!Add up your activities during the day in periods of at least 10 minutes each．Start slowly ..．and build up．If you're already doing some light activities move up to more moderate ones．A little is good, but more is better if you want to achieve health benefits.
Scientists say add up 60 minutes of physical activity every day to stay healthy or improve your health．Time needed depends on effort - as you progress to moderate activities, you can cut down to thirty minutes, four days a week.
Physical activity doesn't have to be very hard to improve your health．This goal can be reached by building physical activities into your daily routine．Just add up in periods of at least ten minutes each throughout the day．After three months of regular physical activity, you will notice a difference - people often say getting started is the hardest part.
(From Handbook for Canada's Physical Activity Guide to Healthy Active Living p．4．Canadian Society for Exercise Physiology, Ottawa, Ontario, 1998) Nowadays people __. A． are less active than in the past
B． are more active than in the past
C． are sitting as much as they used to be
D． are sitting as less as they used to be
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