Identify which statement is true:

A. Isotopes of the same element have the same atomic number and mass number, but a different number of neutrons.
B. Isotopes of the same element have the same mass number and different atomic numbers.
C. Isotopes of the same element have the same number of neutrons and a different number of protons.
D. Isotopes of the same element have the same atomic number and different mass numbers.