In a medium of dielectric constant $K$,the electric field is $\vec E$. If $\varepsilon_0$ is the permittivity of free space,the electric displacement vector is:

$Assertion \; (A)$: 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:

Assertion : In the absence of an external electric field,the dipole moment per unit volume of a polar dielectric is zero.
Reason : The dipoles of a polar dielectric are randomly oriented.

Which of the following statements is false in the case of polar molecules?

The function of a dielectric in a capacitor is

When a dielectric is placed in an external electric field,the electric field inside the dielectric is