The dielectric constant $K$ of an insulator cannot be

$Assertion \; (A)$: Non-polar materials do not have any permanent dipole moment.
$Reason \; (R)$: When a non-polar material is placed in an electric field,the centre of the positive charge distribution of its individual atom or molecule coincides with the centre of the negative charge distribution.
In the light of the above statements,choose the most appropriate answer from the options given below:

What are polar molecules and non-polar molecules? Give examples of both.

Explain the difference in the behaviour of a conductor and a dielectric in the presence of an external electric field.

The dielectric constant of pure water is $81$. Its permittivity will be ........

What is a linear isotropic dielectric?