Question

How many of the following properties is/are used for protecting electrostatic-sensitive instruments?
$I$. Superconductivity
$II$. Electrostatic shielding
$III$. Earthing

Answer 1

Concept of electrostatic shielding: Electrostatic shielding is a method of shielding or protecting a particular region or space or any sensitive building/instrument from the effect of the external field produced by an electric charge.
Thus, by this method we can protect electrostatic sensitive instruments by keeping them inside a conductor, since the surface of conductor is an equipotential surface and electric field inside it is zero.
Hence, 1 property is used.