Assertion : The 19th electron in potassium atom enters 4s-orbital and not 3d orbital.
Reason : The energies of the orbitals can be compared with the help of (n+l) rules.
A. if both assertion and reason are correct and reason is correct explanation for assertion .
B. If both assertion and reason are correct but reason in not correct explanation for assertion.
C. If assertion is correct but reason is incorrect.
D. If both assertion and reason are incorrect.
