Atoms of two different elements must have different electrical charges. numbers of neutrons. atomic numbers. energy levels.

Option (c) is the correct answer.

Explanation:

Each and every atom placed in the periodic table has an atomic number. With the help of this atomic number we get get to know the number of protons each atom holds.

This atomic number helps in determining the respective atom.

Hence, we can conclude that atoms of two different elements must have different  atomic numbers.

i believe the answer is a.