In what way are elements in the same column of the periodic table the same?

In what way are elements in the same column of the periodic table the same? 





A) They have the same number of protons.
B) They have the same number of neutrons.
C) They have the same number of electrons.
D) They have the same number of electrons in their valence shell.
E) They have the same number of electron shells.





Answer: D


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