Let $f ( x ) = \cosh \left( 3 ^ { x } \right)$

Multiple Choice

Let $f ( x ) = \cosh \left( 3 ^ { x } \right)$ Then $f ^ { \prime } ( x )$ is

A) $\ln 3 \sinh \left( 3 ^ { x } \right)$
B) $3 ^ { x } \sinh \left( 3 ^ { x } \right)$
C) $\sinh \left( 3 ^ { x } \right)$
D) $3 ^ { x } \ln 3 \sinh \left( 3 ^ { x } \right)$
E) $- 3 ^ { x } \ln 3 \sinh \left( 3 ^ { x } \right)$