The masses of atoms and molecules can be determined using a mass spectrometer. The masses can be shown as a series of peaks.

Element X exists as a diatomic molecule. The mass spectrum will show the mass of ions from individual atoms of X and from X2 molecules.

The mass spectrum for element X is shown below:

How many different isotopes of X can be determined from this spectrum?

A 1

B 2

C 3

D 4

E 5

The answer is B 2, but I don’t really get it. Any help would be appreciated!