$\text { Find an equation of the line that is tangent to the graph of the function } f ( x ) = \frac { 7 } { \sqrt { x } }$

$\text { Find an equation of the line that is tangent to the graph of the function } f ( x ) = \frac { 7 } { \sqrt { x } }$ and parallel to the line $7 x + 2 y - 18 = 0$ .

A) $7 x + y + 21 = 0$
B) $9 x + y - 18 = 0$
C) $9 x + 2 y + 9 = 0$
D) $7 x + 2 y - 21 = 0$
E) $7 x + 2 y - 14 = 0$