State which of the following sets are finite or infinite :

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

State which of the following sets are finite or infinite :

$\{ x:x \in N$ and $x$ is odd $\} $

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

$\{ x:x$ is a triangle in a plane $\}  \ldots \{ x:x$ is a rectangle in the plane $\} $

$A = \{ x:x \ne x\} $ represents

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

$\{\varnothing\} \subset A$

In the following state whether $A=B$ or not :

$A=\{a, b, c, d\} ; B=\{d, c, b, a\}$