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补全短文：

He has also included symbols to show which ions are nutrients,and which are common in soil or water. ________.

A.There have been many attempts to redesign the periodic table since Dmitri Mendeleev drew it up in 1871.

B.And the size of element's symbol reflects how much of it is found in the Earth's crust.

C.Railsback has still ordered the elements according to the number of protons they have.

D.Raisback has listed some elements more than once.

正确答案：B

答案解析：空格前的这句话是围绕symbol符号来讲述的；选项B也是符号，即：元素符号的大小反映出它在地壳中被发现的量。

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