Question

Two sets $A\&B$ such that $A=\varphi$ and $B=\left\{A\right\}$, then $n\left(B\right)=$

• A. $0$
• B. $1$
• C. $2$

Answer 1

The correct option is B $1$

Given two sets $A\&B$ such that $A$ is an empty set
$\Rightarrow A=\varphi$
Now $B=\left\{A\right\}=\left\{\right\{\left\}\right\}$
This means, $B$ has one element $\varphi$
$\Rightarrow n\left(B\right)=1$