Man's first real inventionand one of the most important inventions in history, was the wheel All transportation and (1)__________________. The wheel is the simplest yet perhaps the most remarkable of all invention. Because there are no wheels in nature--no living things was ever created with wheel How,then,did man come to invent the wheel? Perhaps some early hunters found that they could (2)______________more easily than they could carry it. However,the logs themselves weighed a lost. It must have taken a great prehistoric thinker to imagine two thin slices on log connected at their centers by a strong stick. This would roll along just as the logs did yet be much lighter and easier to handle. Thus the (3)____________________.
every machine in the world depend on it
roll the body of a heavy animal through the forest on logs
wheel and axle came into being and with them the first carts
发表于 2014-1-16 12:02
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发表于 2014-1-20 11:45
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