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補全短文：

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.

正確答案：B

答案解析：空格前的這句話是圍繞symbol符號來講述的；選項B也是符號，即：元素符號的大小反映出它在地殼中被發(fā)現(xiàn)的量。

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