Below is a text with blanks. Click on each blank, a list of choices will appear. Select the appropriate answer choice for each blank.
下面的文本有一些空格。点击每个空格会出现一组选项，请为每个空格选出最合适的答案。
To learn the speech of alchemy, an early form of chemistry in which people attempted to turn metals into gold, it helps to think back to a time when there was no science: no atomic number or weight, no periodic chart, no list of elements. To the , the was not made of leptons, bosons, gluons, and quarks. Instead it was made of , and one substance—say, walnut oil—could be just as as another—say, silver—even though modern scientists would say one is heterogeneous and the other homogeneous. Without knowledge of atomic structures—how would it be to tell elements from compounds?
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