Under this transformation ,the region $D=\{z\in \Bbb C:|z|

Under this transformation ,the region $D=\{z\in \Bbb C:|z|

I am stuck on the following problem:
Under the transformation $w=\sqrt \frac {1-iz}{z-i}$ ,the region $D=\{z\in
\Bbb C:|z|<1 \}$ is transformed to which of the following?
$\{z \in \Bbb C: 0 <\arg z <\pi\}$
$\{z \in \Bbb C: -\pi <\arg z <\pi\}$
$\{z \in \Bbb C: \pi/2 <\arg z <\pi \,\,\text{or}\,\, 3\pi/2<\arg z<2\pi \}$
$\{z \in \Bbb C: 0 <\arg z <\pi/2 \,\,\text{or}\,\, \pi<\arg z<3\pi/2 \}$
Can someone explain? Thanks and regards to all.