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

{–1, 1} {–1, 1, o, –i) {–i, i} None of these

{–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.