Magnetic energy per unit volume is represented by

The correct option is A
B22μ0
Energy stored in an inductor=12LI2
This energy is actually stored in the magnetic field generated by the current flowing through the inductor. In a pure inductor, the energy is stored without loss, and is returned to the rest of the circuit when the current through the inductor is ramped down, and its associated magnetic field collapses.
W=12LI2=μ0N2A2l(Blμ0N)2=B22μ0lA
∴Energy stored per unit volume=B22μ0