Isotopes of the same element must have the same A. atomic number
B. mass number
C. number of nucleons
D. number of neutrons

D. number of neutrons

Explanation:

Isotopes of the same element must have the same number of neutrons. Neutrons of an atom are the uncharged particles within the nucleus.

Isotopy is the existence of two or more atoms of the same element having the same atomic number but having different mass number due to the differences in the number of neutrons in their various nuclei.

Therefore, isotopes differs based on the number of neutrons they contain.

vanderwaal's forces of attraction are the electrostatic intermolecular forces that exist in a molecule due to the temporary or permanent dipoles that are developed in a molecule. in , the major intermolecular forces are dipole-dipole interactions as the molecule is polar (bent structure). so the vanderwaal's forces of interaction in between molecules are the permanent dipole-dipole interactions that develop due to the dipole that exists in between the polar h - s bond. the positively charged hydrogen atom is attracted towards the negative end of the dipole that is sulfur of the adjacent molecule. therefore, these forces of attraction are relatively stronger than that of london dispersion forces that exist in non polar molecules.

i would say b

explanation:

but i think i would need more information than that