Question

What does the Pauli exclusion principle state?
Electrons will be added to an atom at the lowest possible level or sublevel.
An orbital can contain two electrons only if all other orbitals at that sublevel are empty.
An orbital can contain two electrons only if all other orbitals at that sublevel contain at least one electron.
Two electrons occupy the same orbital only if they have opposite spins.
Two electrons occupy the same orbital only if they have same spins.