A. They received advanced education. B. They are truly creative and peace-loving.

C. They didn't turn anything into something great. D. They achieved great success in their fields.

　　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 hide your running shoes,it might be worth giving that crazy idea a go.

　　 According to The Huffington Post,an outdoor run in winter, as opposed to one on a treadmill(跑步机),bums more calories because the body is working hard to regulate(调节)its core temperature. Furthermore, 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 the summer can drag you down and tire you faster, but cold weather is refreshing. It adjusts you to your surroundings,making you feel alive.

　　Of course,the threat of smog in some built-up areas is a further hurdle to winter exercise. Heart attacks stroke, lung cancer and asthma are all dangers of running in smog. The combination 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 car exhaust(尾气) 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 function harder. D. Their body temperature can get lower.

2. How does summer affect runners?

A. It builds up their energy quickly. B. It makes runners tired easily.

C. It lessens runners' stress. D. It causes heart attack.

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

A. Stop driving cars. B. Do more exercise.

C. Avoid outdoor exercise. D. Run late in the morning.

4. What can be the best title of the text?

A. Refresh with a Winter Run B. Take Outdoor Exercise in Summer

C. Go to Run in a Park D. Follow the Tips to Reduce Stress

　　Once you find water, a major issue remains: Is it pure? Is it drinkable? And if not, how to make it drinkable?

You can make a water filter(过滤器) from a cone of birch bark(桦树皮).This cone is then filled with layers of sand, charcoal(木炭), grasses, and other materials. Grasses and sand help to trap suspended particles(悬浮颗粒). Charcoal helps to remove chemical impurities, but not bacteria.You may have to pass the water through the filter more than once, depending on the size of the filter and what it's made of. Generally speaking, the bigger the filter, and the more layers you have in it, the better.