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提问人:网友d*******1 发布时间:2022年4月6日 11:38
[问答题]

工件夹紧后,位置不会再变化,因而也就定位了。这种说法对吗?为什么?

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The recent surge in oil prices to roughly $55 a barrel teaches some useful lessons. One is that surprises happen. A year ago futures contracts predicted today’s price would be $25. A second is that the economy has grown less vulnerable to oil "shocks". Compared with 1973, we now use almost 50 percent less energy for each dollar of output. New industries (software, theme parks) need less than the old (steel, chemicals). But the largest lesson is depressingly familiar. Americans won’t think realistically about oil. We consider cheap fuel a birthright, and when we don’t get it, we whine—rather than ask why or what we should do. If prices rise, we blame a conspiracy of greedy oil companies, OPEC or someone. The reality is usually messier. Energy economist Philip Verleger Jr. attributes the present price run-up to massive miscalculation. Oil companies and OPEC underestimated global demand, particularly from China. Since 2001 China’s oil use has jumped 36 percent. 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