Let z and w be two complex numbers such that $|z| \leq 1, |w| \leq 1$ and $|z+iw|$ = |z-i w}=2$ Then z equals

Question

$\begin{array}{1 1} 1\;or\;i \\ i\;or\;-i \\ 1\;or \;-1 \\ i\;or\;-1 \end{array} $