What an electron and a neutron have in common is that <u>each particle exists inside an atom,</u>
Atoms consist of three particles: protons (which are positively charged), electrons (which are negatively charged), and neutrons (which have no charge).
I believe that number 27 is A
Atomic number shows the number of protons in an atom's nucleus. If the atomic number is 30, then it has 30 protons. The question says it is neutral, so it must have the same amount of protons and electrons.
A is the correct answer based on this.