Solve the Following Equation $\cos 2 x ( 4 \cos x + 2 ) = 0$

Multiple Choice

Solve the following equation.​ $\cos 2 x ( 4 \cos x + 2 ) = 0$ ​

A) $\frac { 4 \pi } { 3 } + n \pi , \frac { 2 \pi } { 3 } + n \pi , \frac { 4 \pi } { 3 } + 2 n \pi$
B) ​ $\frac { \pi } { 4 } + \frac { n \pi } { 2 } , \frac { 2 \pi } { 3 } + 2 n \pi , \frac { 4 \pi } { 3 } + 2 n \pi$
C) ​ $\frac { \pi } { 3 } + n \pi , \frac { \pi } { 3 } + n \pi$
D) ​ $\frac { \pi } { 2 } + n \pi , \frac { 2 \pi } { 5 } + n \pi$
E) ​ $\frac { 2 \pi } { 3 } + n \pi , \frac { 2 \pi } { 3 } + n \pi$