An atom of the isotope sulfur-31 consists of how many protons, neutrons, and electrons? (p = proton, n = neutron, e = electron)

"Isotopes are atoms of same element which have same number of protons but different number of neutrons."

According to the periodic table, Sulfur has the atomic number  as 16.

In the neutral state,
   the number of protons in Sulfur = atomic number
                                                          = 16

    number of electrons = number of protons
    number of electrons    = 16

    Atomic mass = number of protons + number of neutrons
       
     number of neutrons = atomic mass - number of protons
                                     = 31 - 16
                                     = 15

The answer is b because c don't explain why the moths are on them and it isn't a because as we know only one species of moth does this