# The order of $-i$ in the multiplicative group of $4^{th}$ roots of unity is

$\begin{array}{1 1}(1)4&(2)3\\(3)2&(4)1\end{array}$

The roots of fourth roots of unity are
$1.-1,i,-i$
$(-i)^4=i^4=1$
Order of $(-i) =4$
Hence 1 is the correct answer.