单选题
[填句补文]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.