Use the Trigonometric Substitution to Rewrite the Algebraic Expression as a Trigonometric

Multiple Choice

Use the trigonometric substitution to rewrite the algebraic expression as a trigonometric function of $\theta$ , where $0 < x < \frac { \pi } { 2 }$ .
$\sqrt { 16 - x ^ { 2 } } , x = 4 \cos \theta$

A) 16 cos $\theta$
B) 16 sin $\theta$
C) 4 sin $\theta$
D) - 4 sin $\theta$
E) 4 cos $\theta$