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{{B}} Why Humans
Walk on Two Legs{{/B}} A team of scientists that studied chimpanzees (黑猩猩) trained to use treadmills(跑步机) has gathered new evidence suggesting that our earliest apelike ancestors started walking on two legs because it required less energy than getting around on all fours. Michael Sockol, researcher of UC Davis, worked for two years to find an animal trainer willing to coax (劝诱) adult chimps to walk on two legs and to walk on ail fours. The five chimps also wore face masks used to help the researchers measure oxygen consumption. While the chimps worked out, the scientists collected data that allowed them to calculate which method of locomotion (移动) used less energy and why. The team gathered the same information for four adult humans walking on a treadmill. The rese A. where humans came from B. how chimpanzees could be trained to use treadmills C. why our apelike ancestors came to walk on two legs D. when our earliest ancestors began to live in forested areas 更多"{{B}}第三篇{{/B}}"的相关试题: [单项选择]第三篇
Water
The second most important constituent (构成成份) of the biosphere (生物圈) is liquid water. This can only exist in a very narrow range of temperatures, since water freezes at 0℃ and boils at 100℃. Life as we know it would only be possible on the surface of a planet which had temperatures somewhere within this narrow range.
The earth’s supply of water probably remains fairly constant in quantity. The total quantity of water is not known very accurately, but it is about enough to cover the surface of the globe to a depth of about two and three-quarter kilometers. Most of it is in the form of the salt water of the oceans about 97 percent. The rest is fresh, but three quarters of this is in the form of ice at the Poles and on mountains, and cannot be used by living systems until melted. Of the remaining fractional which is somewhat less than one per cent of the whole, there is 10—20 times as much stored underground water as t
A. in the center of the earth. B. on the surface of our planet. C. in a very narrow range of temperatures. D. in the coastal areas of the earth. [单项选择]{{B}}第三篇{{/B}}
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