Rationalize the Denominator and Simplify $\frac { 1 } { \sqrt { 7 x } }$

Rationalize the denominator and simplify. Assume that all variables represent positive real numbers.
- $\frac { 1 } { \sqrt { 7 x } }$

A) $\sqrt { 7 x }$
B) 1
C) $\frac { \sqrt { 7 x } } { 7 x }$
D) $\frac { \sqrt { 7 x } } { 49 x ^ { 2 } }$