To identify the quantity with different dimensions, we analyze the dimensional formula for each option:

1. Energy per unit volume: This is known as Energy Density. $\frac{\text{Energy}}{\text{Volume}} = \frac{[ML^2T^{-2}]}{[L^3]} = [ML^{-1}T^{-2}]$

2. Force per unit area: This is the definition of Pressure or Stress. $\frac{\text{Force}}{\text{Area}} = \frac{[MLT^{-2}]}{[L^2]} = [ML^{-1}T^{-2}]$

3. Product of voltage and charge per unit volume: The product of Voltage ($V$) and Charge ($q$) is Work or Energy ($W = Vq$). $\frac{\text{Voltage} \times \text{Charge}}{\text{Volume}} = \frac{\text{Energy}}{\text{Volume}} = [ML^{-1}T^{-2}]$

4. Angular momentum per unit mass: Angular Momentum ($L$) has dimensions $[ML^2T^{-1}]$. Mass ($m$) has dimensions $[M]$. $\frac{\text{Angular Momentum}}{\text{Mass}} = \frac{[ML^2T^{-1}]}{[M]} = [L^2T^{-1}]$

Conclusion: Options A, B, and C all possess the dimensions $[ML^{-1}T^{-2}]$. Option D has dimensions $[L^2T^{-1}]$, which is different.