Q: Different isotopes of an element have different mass numbers because they have different numbers of what?


Read this paragraph and choose the correct option from the provided answers:

An atom’s mass number is its mass in atomic mass units (amu), which is about equal to the total number of protons and neutrons in the atom. Different isotopes of an element have different mass numbers because they have different numbers of neutrons.

 Choices:

- protons

- electrons

- nuclei

- neutrons


A:
neutrons