Answer : The correct option is, neutrons
Explanation :
Isotope : It is defined as the element that have the same number of protons but have the different number of neutrons of each of the atom.
Atomic number is defined as the number of protons or number of electrons.
Atomic number = number of protons = number of electrons
Mass number is defined as the sum of number of protons and number of neutrons.
Number of neutrons = Mass number - Number of protons
For example : Carbon - 13 isotope has mass number = 13, atomic number = 6 and the number of neutrons = 13 - 6 = 7
Hence, the isotopes of the same element have different numbers of neutrons.
