Which diagram shows electrons violating the pauli exclusion principle?

Correct Option C

Reason:
The Pauli Exclusion Principle states as 'in an atom or molecule, no two electrons can have the same four electronic quantum numbers. Further, an orbital can contain a maximum of only two electrons, the two electrons must have opposing spins.'

Thus, it can be seen that in option C, electrons in last 2 subshell have electrons with same spin, which is a violation of Pauli Exclusion Principle .