If $A=\left\{x \in C: x^2=1\right\}$ and $B=\left\{x \in C: x^4=1\right\}$, then $A \Delta B$ is equal to

{–i, i}

$x^2=1 \Rightarrow x=-1,1$         ∴ $A =\{-1,1\}$

$x^4=1 \Rightarrow x^2=-1,1$

$\Rightarrow x=-i, i,-1,1 . B=\{-i, i,-1,1\} $

∴  $A \Delta B=(A-B) \cup(B-A)=\varphi \cup\{-i, i\}=\{-i, i\}$

Hence (3) is the correct answer.