Rewrite the Expression in Terms of Exponentials and Simplify the Results

Multiple Choice

Rewrite the expression in terms of exponentials and simplify the results.
- $\ln ( \cosh 4 x - \sinh 4 x )$

A) $- 4 x$
B) $\ln \left( e ^ { 4 x } - e ^ { - 4 x } \right)$
C) $- 8 x$
D) $- 4$