Correct option is D because Explanation for Correct Option:


Dipole moment is the product of the magnitude of the charge and the distance between the centers of the positive and negative charges
In 1, 2 dichlorobenzene the two dipoles are at 60 Degree (i.e. unsymmetric).
Thus possesses dipole moment.

**Dipole Moment**

The dipole moment is a measure of the polarity of a bond or a molecule. It is a vector quantity that indicates the separation of positive and negative charges within a molecule. The dipole moment is determined by the difference in electronegativity between the atoms involved in the bond and the bond length.

**Explanation of options**

a) trans-2, 3-dichloro-2-butene
- In this molecule, there are two chlorine atoms attached to the double bond. The dipole moments of the two C-Cl bonds cancel each other out due to the trans configuration, resulting in a net dipole moment of zero.

b) trans-1, 2-dinitroethene
- This molecule also has a trans configuration, but the presence of two nitro groups (-NO2) on the double bond makes it highly polar. The nitro groups have a high electronegativity, causing the molecule to have a significant dipole moment.

c) 1, 4-dichlorobenzene
- In this molecule, there are two chlorine atoms attached to the benzene ring. The dipole moments of the two C-Cl bonds cancel each other out due to the symmetrical arrangement of the chlorine atoms, resulting in a net dipole moment of zero.

d) 1, 2-dichlorobenzene
- In this molecule, the two chlorine atoms are attached to adjacent carbon atoms on the benzene ring. Due to the asymmetrical arrangement of the chlorine atoms, the dipole moments of the two C-Cl bonds do not cancel each other out. As a result, the molecule has a net dipole moment.

**Conclusion**
The correct answer is option 'D', 1, 2-dichlorobenzene, because it has an asymmetrical arrangement of the chlorine atoms, resulting in a non-zero net dipole moment.