Can anyone answer this question?

Hello! Those are called the isotopes of those elements!! They have more than just one form and each has it’s own AMU’s so the multiple numbers above different elements, represent the isotopes of those elements. Carbon is a good one just for one example.

Hope this helps you out! Questions please just ask! Thanks!

Ibelieve its a because an empirical formula usually has a ch in it your options are a or b