如图所示，把正在发声的闹钟放在玻璃罩内，闹钟和罩的底座之间垫上柔软的泡沫塑料，逐渐抽出罩内的空气，闹钟的声音会逐渐变小，直至听不到声音．这个实验说明了（　　）

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    There are times when people are so tired that they fall asleep almost anywhere.We can see there is a lot of sleeping on the bus or train on the1home from work in the evenings.A man will be2the newspaper,and seconds later it3as if he is trying to4it.Or he will fall asleep on the shoulder of the stranger5next to him.6place where unplanned short sleep7is in the lecture hall where a student will start snoring（打鼾）so 8that the professor has to ask another student to9the sleeper awake.A more embarrassing（尴尬）situation occurs when a student starts falling into sleep and the10of the head pushes the arm off the11,and the movement carries the 12of the body along.The student wakes up on the floor with no13of getting there.The worst time to fall asleep is when14.Police reports are full of15that occur when people fall into sleep and go16the road.If the drivers are 17,they are not seriously hurt.One woman's car,18,went into the river.She woke up in four feet of19and thought it was raining.When people are really20nothing will stop them from falling asleep—no matter where they

are.

有观点认为，“农民战争从来只是一种改朝换代的工具，太平天国仍然是旧式农民战争，但已萌发了一些新苗……”。下列与之结论最为相符的是

①x₁=2，x₂=3；②m> ；③二次函数y=（x-x₁）（x-x₂）+m的图象与x轴交点的坐标为（2，0）和（3，0）．

其中正确的结论是____（填正确结论的序号）