Why electric field intensity inside hollow spherical charged conductor is zero

A positive point charge $Q$ is kept (as shown in the figure) inside a neutral conducting shell whose centre is at $C$. An external uniform electric field $E$ is applied. Then,

(i) inside the shell,

A solid conducting sphere of radius $a$ is surrounded by a thin uncharged concentric conducting shell of radius $2a$. A point charge $q$ is placed at a distance $4a$ from common centre of conducting sphere and shell. The inner sphere is then grounded.

Pick up the correct statement.

The figure shows a charge $q$ placed inside a cavity in an uncharged conductor. Now, if an external electric field is switched on, then

Represent the union of two sets by Venn diagram for each of the following.

$X=\{x | x$ is a prime number between $80$ and $100\}$

$Y=\{y | y$ is an odd number between $90$ and $100\}$

In the figure, a solid sphere of the radius $a=2.00 \mathrm{cm}$ is concentric with a spherical conducting shell of inner radius $b=2.00a$ and outer radius $c=2.40a$. The sphere has a net uniform charge $q_1=+5.00 \mathrm{C}$, the shell has a net charge $q_2=-q_1$. What is the magnitude of the electric field at radial distances$r=2.30 a$?