Transition of electron between `p_x` and `p_y` would not lead to an spectral line.
p-orbitals are degenerate orbitals.
A. If both assertion and reason are true and the reason is the correct explanation of the assertion.
B. If both assertion and reason are true but reason is not the correct explanation of the assertion.
C. If assertion is true but reason is false
D. If assertion is false but reason is true.