Answer:
Option A
Step-by-step explanation:
Hund's rule expresses each orbital in a sub-shell is independently occupied with one electron before any one orbital is doubly involved, and all electrons in separately involved orbitals have a similar turn.
It expresses that when filling degenerate orbitals, electrons fill them separately first , with parallel spin. This is the aftereffect of a molecule's propensity to locate the most reduced energy state conceivable.