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  3. The polar vortex (极地旋风) currently sweeping across the North American contine

The polar vortex (极地旋风) currently sweeping across the North American contine

游客2024-03-07  48
问题     The polar vortex (极地旋风) currently sweeping across the North American continent is bringing with the scenes usually associated with the Arctic or Antarctic. Massive snowfall and violent winds have brought temperatures down to record lows. In some areas of the US, such as the state of Indiana, all but essential emergency vehicles are banned from the roads. People are being urged to remain inside in the warm.
    The human body is not designed for polar cold—most of us live in temperate and tropical climate, where the mercury rarely dips below freezing. There are populations that have adapted to polar extremes—like the Inuit in Arctic Canada and tribes like the Nenets in the north of Russia—but the vast majority of Homo sapiens (现代入) has no experience of living in such sub-zero temperatures. And while our ingenuity and expertise has allowed us to create clothing to withstand all but the most violent Arctic blizzards, polar survival is all about keeping out of the most fearsome cold unless you absolutely have to.
    What happens when we get cold? The human body has several defence mechanisms to try and boost our core temperature when it gets chilly. Our muscles shiver and teeth chatter. Our hairs rise and our flesh forms "goosebumps"—a kind of evolutionary echo from the times when our ancestors were covered in fur. The hypothalamus (下丘脑) , the gland in the brain that acts as your body’s thermostat (恒温器) , stimulates these reactions to keep the body’s vital organs warm, at least until it can find some kind of warmth and shelter.
    The hypothalamus’s mission is to keep the core warm at all costs—sacrificing the extremities if need be. That’s why we feel pins and needles in our fingers and toes in extreme cold—the body is keeping its warm blood close to the centre, constricting blood supply in the outer regions such as the end of our limbs. In extreme cold, and especially if bare skin is open to the elements, this effect can end in frostbite.
    So how do other warm-blooded animals living in such climate cope when we can’t? Polar animals are either covered in winter coats of fur—which traps warm air close to the body—or else large quantities of fat, sometimes inches thick. Fat does not transfer heat very well, so it keeps it inside the body. Humans, with naked skin and relatively little fat, just aren’t built for these environments.
    But we have learned to imitate these qualities. Scientists in Antarctic stations, for instance, dress in layers upon layers, which traps warm air close to the body like fur does. [br] How does human body keep the core warm in extreme cold according to the passage?
选项 A、Constrict blood supply to the centre.
B、Reduce blood flow in the outer regions.
C、Keep its warm blood close to the skin.
D、Speed up the body’s blood flow.
答案 B
解析 细节题。根据题干中的keep the core warm可定位到第四段。该段第一、二句提到下丘脑的任务是不惜一切代价保持人体核心温度，因此在极寒天气中，人们会感到手脚发麻，这时，人体让温暖的血液保持在人体核心器官附近，限制人体外围的血液流动，因此B项表述符合原文，故选B。
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