Which of the following are sets ? Justify your answer.

The collection of questions in this chapter.

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

$\{ \{ 3,4\} \}  \subset A$

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

The set of numbers which are multiple of $5$

Examine whether the following statements are true or false :

$\{ x:x$ is an even natural number less than $6\}  \subset \{ x:x$ is a natural mumber which divide $36\} $

List all the elements of the following sers :

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

Which of the following are examples of the null set

Set of even prime numbers