Let $f(x)=\cos (7 x)$ And $g(x)=\sqrt{1-x^{2}}$ What Is $g(f(x))$ ?
A) $\sin (7 x)$

Multiple Choice

Let $f(x) =\cos (7 x)$ and $g(x) =\sqrt{1-x^{2}}$ . What is $g(f(x) )$ ?

A) $\sin (7 x)$
B) $-\sin (\sqrt{7} x)$
C) $\sqrt{\cos (49 x) -1}$
D) $\cos \left(7 \sqrt{x^{2}-1}\right)$