Which of the Following Is the Equation of the Line $y = \sqrt { x }$

Multiple Choice

Which of the following is the equation of the line tangent to the curve $y = \sqrt { x }$ at $x = 9$ ?
(I) y = -x - $\frac { 1 } { 6 }$
(II) y = $\frac { 1 } { 2 }$ x + 3
(III) y = $\frac { 1 } { 6 }$ x + $\frac { 3 } { 2 }$
(IV) y = $\frac { 1 } { 2 }$ $x ^ { - 1 / 2 }$ - $\frac { 1 } { 6 }$

A) IV
B) III
C) I
D) II
E) none of these