Which of the Following Is Equal to Limit $\lim _ { x \rightarrow 0 } \left( \frac { 1 - e ^ { x } } { 1 + e ^ { 3 x } } \right)$

Multiple Choice

Which of the following is equal to limit $\lim _ { x \rightarrow 0 } \left( \frac { 1 - e ^ { x } } { 1 + e ^ { 3 x } } \right)$ ?

A) -1
B) 0
C) 1
D) $e$
E) Does not exist