Solve the Equation and Express the Solution in Exact Form $\ln 3 x + \ln 9 x = \ln 28$

Multiple Choice

Solve the equation and express the solution in exact form.
- $\ln 3 x + \ln 9 x = \ln 28$

A) $\{ 1 \}$
B) $\left\{ \frac { \mathrm { e } ^ { 28 } } { 27 } \right\}$
C) $\left\{ \left( \frac { 28 } { 27 } \right) ^ { 1 / 2 } \right\}$
D) $\{ 0 \}$