Let $x ( t ) = 1 - e ^ { t } , y ( t ) = 1 + e ^ { t }$

Multiple Choice

Let $x ( t ) = 1 - e ^ { t } , y ( t ) = 1 + e ^ { t }$ be the parametric equations of a curve. Then $\frac { d y } { d x }$ is

A) $e ^ { t }$
B) $e ^ { - t }$
C) -1
D) 1
E) $1 - e ^ { t }$