A.\(\int {f\left( x \right)dx} = \dfrac{1}{2}\ln \left| {3x + 1} \right| + C\)
B.\(\int {f\left( x \right)dx} = \dfrac{1}{3}\ln \left| {3x + 1} \right| + C\)
C.\(\int {f\left( x \right)dx} = \dfrac{1}{3}\ln \left( {3x + 1} \right) + C\)
D.\(\int {f\left( x \right)dx} = \ln \left| {3x + 1} \right| + C\)