State which of the following sets are finite or infinite :

$\{ x:x \in N$ and ${x^2} = 4\} $

List all the elements of the following sers :

$C = \{ x:x$ is an integer ${\rm{; }}{x^2} \le 4\} $

Let $A=\{1,2,\{3,4\}, 5\} .$ Which of the following statements are incorrect and why ?

$\{ 3,4\}  \in A$

Let $A=\{1,2,\{3,4\}, 5\} .$ Which of the following statements are incorrect and why ?

$\varnothing \subset A$

Write the following sets in roster form :

$C = \{ x:x{\rm{ }}$ is a two-digit natural number such that sum of its digits is $8\} $

State whether each of the following set is finite or infinite :

The set of numbers which are multiple of $5$