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  3. Throughout the history of life, species of living creatures have made use of chemical energy by the slow combination of certain

Throughout the history of life, species of living creatures have made use of chemical energy by the slow combination of certain

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问题     Throughout the history of life, species of living creatures have made use of chemical energy by the slow combination of certain chemicals with oxygen within their cells. The process is analogous to combustion, but is slower and much more delicately controlled. Sometimes use is made of energy available in the bodies of stronger species as when a remora hitches a ride on a shark or a human being hitches an ox to a plough.
    Inanimate sources of energy are sometimes used when species allow themselves to be carried or moved by wind or by water currents. In those cases, though, the inanimate source of energy must be accepted at the place and time that it happens to be and in the amount that happens to exist.
    The human use of fire involved an inanimate source of energy that was portable and could be used wherever desired. It could be ignited or extinguished at will and could be used when desired. It could be kept small of feed till it was large, and could be used in the quantities desired.
    The use of fire made it possible for human beings, evolutionarily equipped for mild weather only, to penetrate the temperate zones. It made it possible for them to survive cold nights and long winters, to achieve security against fire-avoiding predators, and to roast meat and grain, thus broadening their diet and limiting the danger of bacterial and parasitic
infestation.
    Human beings multiplied in number and that meant there were more brains to plan future advances. With fire, life was not quite so hand-to-mouth; and there was more time to put those brains to work on something other than immediate emergencies.
    In short, the use of fire put into motion an accelerating series of technological advances.
    About 10,000 years ago, in the Middle East, a series of crucial advances were made. These included the development of agriculture, herding, cities, pottery, metallurgy, and writing. The final step that of writing, took place in the Middle East about 5,000 years ago.
    This complex of changes stretching over a period of 5,000 years introduced what we call civilization, the name we give to a settled life, to a complex society in which human beings are specialized for various tasks.
    To be sure other animals can build complex societies and can be composed of different types of individuals specialized for different tasks. This is most marked in such social insects as bees, ants, and termites where individuals are in some cases physiologically specialized to the point where they cannot eat, but must be fed by others. Some species of ants practice agriculture and grow small mushroom gardens, while others herd aphids; still others war on and enslave smaller species of ants. And, of course, the beehive and the ant or termite colony have many points of analogy with the human city.
    The most complex nonhuman societies’, those of the insects, are, however, the re-suit of instinctive behaviour, the guidelines of which are built into the genes and nervous systems of the individuals at birth. Nor does as any nonhuman society make use of fire. With insignificant exceptions, insect societies are run by the energy produced by the insect body.
    It is fair, then, to consider human societies as basically different from other societies and to attribute what we call civilization to human societies only.
Judging from the context, the phrase "hand-to-mouth" (Line 2, Para. 5) most probably means______.
选项 A、adventurous
B、unhappy
C、wandering
D、unstable
答案D
解析 hand—to-mouth的意思是“过一天算一天，勉强糊口”。因此D项unstable“不牢固的，不稳定的”正确。
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