The Derivative Of $f ( x ) = \sqrt { x } - 4$

Multiple Choice

The derivative of $f ( x ) = \sqrt { x } - 4$ at x = 4 is

A) -4
B) $- \frac { 1 } { 4 }$
C) $- \frac { 1 } { 2 }$
D) $\frac { 1 } { 4 }$
E) $\frac { 1 } { 2 }$