have the same number of protons. share the same atomic structure. have similar physical characteristics. share the same number of neutrons.
I gave my students this multiple choice question: Elements in the same column of the Periodic Table of the Elements all

Only one answer is correct among these 4 choices:
- have the same number of protons.
- share the same atomic structure.
- have similar physical characteristics.
- share the same number of neutrons.

Could you tell me which one is correct?

have similar physical characteristics.