Let $f ( x ) = \tanh ( \sin x )$

Multiple Choice

Let $f ( x ) = \tanh ( \sin x )$ Then $f ^ { \prime } ( x )$ is

A) $\operatorname { sech } ^ { 2 } ( \cos x )$
B) $- \cos x \operatorname { sech } ^ { 2 } ( \sin x )$
C) $- \operatorname { sech } ^ { 2 } ( \cos x )$
D) $\cos x \operatorname { sech } ^ { 2 } ( \sin x )$
E) $\sin x \operatorname { sech } ^ { 2 } ( \cos x )$