be used for treating water in
if two electrons have the same n, the same ℓ, and the same ml, then they are in the same orbital. the pauli exclusion principle states that no two identical fermions (a fancy word for electrons and other subatomic particles like electrons) may occupy the same quantum state in an atom simultaneously.
the answer is the first option
just googled it m8. not that hard
particle p is an electron and particle q is a neutron
the answer would be b i believe