Assertion (A) : Energy per unit volume and angular momentum can be...

The unit of energy per unit volume is,

$\dfrac{J}{{m}^{3}} = J{m}^{- 3}$ means, $kg{m}^{- 1}{s}^{- 2}$ and the unit of angular momentum, $mvr = kg{m}^{2}{s}^{- 1}$ are not same so they can not be added, so we can say that same unit quantities can be added and subtracted and same unit quantities have same dimension.