Giải phương trình \({\rm{sin3}}x - \sin x = 0\).

A. \(\left[ \begin{array}{l}x = k\pi \\x = \dfrac{\pi }{4} + k\pi \end{array} \right.\)

B. \(\left[ \begin{array}{l}x = k\pi \\x = \dfrac{\pi }{2} + k\pi \end{array} \right.\) 

C. \(\left[ \begin{array}{l}x = k\dfrac{\pi }{2}\\x = \dfrac{\pi }{2} + k\pi \end{array} \right.\) 

D. \(\left[ \begin{array}{l}x = k\pi \\x = \dfrac{\pi }{4} + k\dfrac{\pi }{2}\end{array} \right.\)