In nickel-78, there are 28 protons, 28 electrons, and 50 neutrons.
The protons is always the atomic number.
The electron would always be the atomic number when it's a neutral atom. (Different for isotopes)
The neutrons is always the number that makes up the mass with protons. You can figure it out by subtracting atomic mass by protons. (78-28 = 50)
The answer is A i think from the options though the answers are worded a bit weird