题型:阅读理解 题类:模拟题 难易度:普通
河北省保定市2020届高三上学期英语摸底考试试卷
In 1953, a mountain climber reported seeing a bar-headed goose soar over the peak of Mount Everest (珠穆朗玛). It was thought impossible. Now researchers who raised 19 of the geese—named for the black stripes on the backs of their heads—have shown the birds really fly so high.
The team trained the youngsters to fly in a large wind tunnel wearing backpacks and face masks full of sensors that recorded their heart rate. blood oxygen levels, temperature, and metabolic rate—how many calories they burned per hour. The researchers simulated(模拟)10w-, medium-, and high-altitude conditions by altering the concentration of oxygen supplied to face masks worn by each goose as it flew in the tunnel.
Birds already have a better heart and lungs than mammals for sustained physical activity. And researchers knew that bar-headed geese have even larger, thinner lungs that let them breathe more deeply and an even bigger heart to pump more oxygen to muscles than other birds.
The wind tunnel experiments showed that when the concentration of oxygen was at its lowest-like the 7% found on top of Mount Everest versus 21% at sea level—the geese's heart rate and frequency of wing beats remained the same even as their metabolic rate dropped. Somehow, the birds managed to cool down their blood-the measured blood temperature dropped so it could take in more oxygen, the researchers report today in eLife. This cooling likely helps compensate for the very thin air, the team says.
Although well trained, the birds were only willing to stay in the air a few minutes-or less when wearing their backpacks and flying at 6ihigh" altitudes. So it's not clear whether these adaptations alone are what make it possible to fly the 8 hours it takes to climb over Mount Everest. But those few minutes showed these geese really could fly over the top of Mount Everest.
根据短文理解,选择正确答案。
AT
TV Ears has helped thousands of people with various degrees of hearing loss hear the television clearly without turning up the volume and now it's better and more affordable than ever! With TV Ears wireless technology, you set your own headset volume, while other TV listeners hear the television at a volume level that's comfortable for them. You can even listen through the headset only and put the TV on mute(静音) if the situation calls for a quiet environment — maybe the baby is sleeping. Or perhaps you are the only one who is interested in listening to the ballgame.
TV Ears patented technology includes a revolutionary noise reduction car tip, not used in any other commercially available headset. This tip reduces outside noise so that television dialogue is clear and understandable. Get the technology that has proven to help the most demanding customers. That's why TV Ears has earned the trust and confidence of audiologists(听觉学家) nationwide as well as world-famous doctors.
Revolutionary TV Ears
Doctor Recommended TV Ears! “My wife and I have used TV Ears almost daily for the past two years and find them a great help in our enjoyment of television. As a retired ear doctor, I heartily recommend TV Ears to people with normal hearing as well as those with hearing loss.” — Robert Forbes, M. D. , CA |
Customer Recommended TV Ears! “Now my husband can have the volume as loud as he needs and I can have the TV at my hearing level. TV Ears is so comfortable that Jack forgets he has them on! He can once again hear and understand the dialogue.” — Darlene & Jack B, CA |
Risk Free Trial! TV Ears comes with a 30-day risk free trial.
Special Offer — Now$59.95.
If you're not satisfied, return it.
Money-back guarantee!
Call now! 800-123-7832
试题篮