If $z = x + i y$ is a complex number such that $\left| \frac { z - i } { z + i } \right| < 1$, then we must have (A) $x > 0$ (B) $x < 0$ (C) $y > 0$ (D) $y < 0$.
If $z = x + i y$ is a complex number such that $\left| \frac { z - i } { z + i } \right| < 1$, then we must have\\
(A) $x > 0$\\
(B) $x < 0$\\
(C) $y > 0$\\
(D) $y < 0$.