Questions are based on the recording you have just heard.
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Now let's continue our topic. Moving rocks, you may have heard about them. It's quite a mystery. Death Valley is a desert plain, a dry lake bed in California surrounded by mountains and on the desert floor these huge rocks, some of them hundreds of pounds. And they move. But nobody has been able to figure out how they are moving because no one has ever seen it happen.[20] Now there are a lot of theories, but all we know for sure is that people aren't moving the rocks. There are no footprints, no type tracks and no heavy machinery.., uh,nothing was ever brought in to move these heavy rocks.
So what's going on? Theory No.1--Wind. Some researchers think powerful uh...windstorms might move the rocks. Most of the rocks move in the same direction as the dominant wind pattern from southwest to northeast. But some, and this is interesting, move straight west while some zigzag or even move in large circles.
Harm...How can that be?
How about wind combined with rain? The ground of this desert is made of clay. It's a desert, so it's dry. But when there is the occasional rain, the clay ground becomes
extremely slippery. Some scientists theorized that perhaps when the ground is slippery the high winds can then move the rocks. There's a problem with this theory. One team of scientists flooded an area of the desert with water, then try to establish how much wind force would be necessary to move the rocks. [21] And get this: you need winds of at least five hundred miles an hour to move just the smallest rocks! And winds that strong have never been recorded. Ever! Not on this planet. So I think it's safe to say that that issues has been settled.
Here is another possibility--ice. It's possible that rain on the desert floor could turn to thin sheets of ice when temperatures drop at night. So if rocks...uh become embedded in ice, uh ... OK, could a piece of ice with rocks in it be pushed around by the wind? But there's a problem with this theory, too. Rocks trapped in ice together would have moved together when the ice moved. But that doesn't always happen.
There are a few other theories. Maybe the ground vibrates, or maybe the ground itself is shifting, tilting.[22] I bet you are saying to yourself well, why don't scientists just set up video cameras to record what actually happens? Thing is, this is a protected wilderness area. So by law that type of research isn't allowed. Besides, in powerful windstorms, sensitive camera equipment would be destroyed.
So all this leads back to my main point -- you need to know about more than just rocks as geologists.
【预测】选项均为描述the rocks的句子，结合其中重复出现的move以及cannot，never和in circles可知，本题可能考查岩石的移动方式或特点。
【解析】D。录音中教授明确提到，现在有很多关于岩石移动的理论，但我们唯一能确定的是人类没有移动过这些石头，故答案为D。