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Compared to the volume of its nucleus,the volume of an atom is about
Q2: What do astronomers mean by light pollution?<br>A)Light
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Q21: Which is the densest planet in the
Q31: During the Dark Ages in Europe,the scientific
Q37: When light reflects off an object,what is
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Q49: Ridges in the middle of the ocean
Q93: Ancient people who knew the Saros cycle
Q105: What is an astronomical unit?<br>A)the average speed
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