D

Step 1: Let's analyze the dimensions of each set of quantities.
Option A:
- Potential difference (V): Dimension $[M^1 L^2 T^{-3} I^{-1}]$
- EMF (Electromotive Force): Dimension $[M^1 L^2 T^{-3} I^{-1}]$
- Voltage: Dimension $[M^1 L^2 T^{-3} I^{-1}]$
All three have the same dimension.

Option B:
- Pressure: Dimension $[M^1 L^{-1} T^{-2}]$
- Stress: Dimension $[M^1 L^{-1} T^{-2}]$
- Young's Modulus: Dimension $[M^1 L^{-1} T^{-2}]$
All three have the same dimension.

Option C:
- Heat: Dimension $[M^1 L^2 T^{-2}]$
- Energy: Dimension $[M^1 L^2 T^{-2}]$
- Work-done: Dimension $[M^1 L^2 T^{-2}]$
All three have the same dimension.

Option D:
- Dipole moment: Dimension $[M^1 L^2 T^{-2} I^{-1}]$
- Electric flux: Dimension $[M^1 L^2 T^{-4} I^2]$
- Electric field: Dimension $[M^1 L^1 T^{-3} I^{-1}]$
Here, the dimensions differ:
Dipole moment: $[M^1 L^2 T^{-2} I^{-1}]$
Electric flux: $[M^1 L^2 T^{-4} I^2]$
Electric field: $[M^1 L^1 T^{-3} I^{-1}]$
Therefore, Option D has different dimensions.

Final Conclusion: The group that has different dimensions is Option D.