Make correct statements by filling in the symbols $\subset$ or $ \not\subset $ in the blank spaces:

$\{ x:x$ is a student of class $\mathrm{XI}$ of your school $\}  \ldots \{ x:x$ student of your school $\} $

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

$1 \in A$

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

$\{1,2,5\}\in A$

Examine whether the following statements are true or false :

$\{ a\}  \in \{ a,b,c\} $

Write the following intervals in set-builder form :

$\left[ { - 23,5} \right)$

Which of the following are sets ? Justify your answer.

The collection of questions in this chapter.