1 . It’s cold and dark outside, and your bed is so warm and comfortable. Going for a run seems like such a bad idea. But before you put your running shoes away, it might be worth giving that crazy idea a try.

According to The Huffington Post，an outdoor run in winter, instead of running on a treadmill (跑步机), burns more calories (卡路里) because the body is working hard to regulate (调节) its temperature. Besides, research shows that race times are faster in cold weather than in warmer temperatures—and quicker runs burn more calories. Similarly, cold weather also makes the heart work harder to distribute blood through the body, making that vital muscle even stronger.

Outdoor exercise also turns up your energy and rids you of the stress and depression that build up every day. The heat and humidity in summer can drag you down and tire you faster, but cold weather is refreshing. It adjusts you to your surroundings, making you feel energetic.

Of course, the threat of smog in some built­up areas is a further problem to winter exercise. Heart attacks, strokes and lung cancer are all dangers of running in smog. The combination (结合) of air pollution and exercise increases the potential problems. If you do choose to run outside on smoggy days, take a path in a park or residential area to avoid polluted air, and go early in the morning, before rush hour. But staying inside on smoggy days and waiting for the next clear day to run is best.

1. How does cold weather benefit runners compared with warm weather?

A．They can run more slowly.	B．They can take in more calories.
C．Their hearts can work harder.	D．Their body temperature can get lower.

2. How does summer affect runners?

A．It makes runners tired easily.	B．It builds up their energy quickly.
C．It lessens runners’ stress.	D．It causes heart attacks.

3. What are the runners supposed to do on smoggy days?

A．Stop driving cars.	B．Run late in the morning.
C．Do more exercise.	D．Avoid outdoor exercise.

4. Which of the following opinion will be supported by the writer?

A．We can refresh ourselves with a winter run.

B．We should go to run in a park everyday.

C．It’s much better to take outdoor exercise in summer.

D．We’d better run on treadmill to reduce stress.