$\text { Find } \lim _{h \rightarrow 0} \frac{f(x+h)-f(x)}{h} \text { for } f(x)=\sqrt{x-7} \text {. }$

Multiple Choice

$\text { Find } \lim _{h \rightarrow 0} \frac{f(x+h) -f(x) }{h} \text { for } f(x) =\sqrt{x-7} \text {. }$

A) $\frac{1}{7 \sqrt{x-7}}$
B) $\frac{1}{2 \sqrt{x-7}}$
C) $\frac{\sqrt{x-7}}{2}$
D) $\sqrt{x-7}$
E) limit does not exist