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更多“驼峰调车场轨道区段的划分应根据调车场线路的布置情况及()作业…”相关的问题
第7题
All that we really need to plot out the future of our universe are a few good measurements
. This does not mean that we can sit down today and outline the future course of the universe with anything like certainty. There are still too many things we don't know about the way the universe is put together. But we do know exacdy what information we need to fill in our knowledge, and we have a pretty good idea of how to go about getting it. Perhaps the best way to think of our present situation is to imagine a train coming into a switchyard(调车场). All of the switches(转辙器) are set before the train arrives, so that its path is completely determined. Some switches we can see, others we cannot. There is no ambiguity if we can see the setting of a switch; we can say with confidence that some possible futures will not materialize and others will. At the unseen switches, however, there is no such certainty. We know the train will take one of the tracks leading out, but we have no idea which one. The unseen switches are the true decision points in the future, and what happens when we arrive at them determines the entire subsequent course of events.
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When we think about the future of the universe, we can see our "track" many billions of years into the future, but after that there are decision points to be dealt with and possible fates to consider. The goal of science is to reduce the ambiguity at the decision points and find the true road that will be followed.
According to the passage, it is difficult to be certain about the distant future of the universe because we______.
A．have too many conflicting theories
B．do not have enough funding to continue our research
C．are not sure how the universe is put together
D．have focused our investigations on the moon and planets
第9题
冰雪天气动车组转向架结冰需要列车限速时，无砟轨道区段限速250km£¯h及以下，有砟轨道区段限速（)及以下。
A.20km/h
B.160km/h
C.200km/h
D.250km/h
