The answer is going to be c
The atoms of elements can gain or lose electrons and become ions. Ions are charged particles that have gained or lost electrons. The atoms of elements can gain or lose electrons to form monatomic ions (made from a single atom of an element).
A potassium atom has a higher proton number meaning that it has more protons and electrons. Due to the Octet Rule, the more electrons an atom has the more shells it has and so will be bigger in size.
Hope this was helpful x
The cells in it are very similar, very few differences
Galactic is referring to the galaxy and cosmos! :)