Tìm các họ nghiệm của phương trình \({\cos ^2}x + {\cos ^2}2x + {\cos ^2}3x + {\cos ^2}4x = 2\)

A. \(\left[ \begin{array}{l} x = \frac{\pi }{2} + k\pi \\ x = \frac{\pi }{4} + k\frac{\pi }{2}\\ x = \frac{\pi }{{10}} + k\frac{\pi }{5} \end{array} \right.\left( {k \in Z} \right)\)

B. \(\left[ \begin{array}{l} x = - \frac{\pi }{2} + k\pi \\ x = \frac{\pi }{4} + k\frac{\pi }{2}\\ x = \frac{\pi }{{10}} + k\frac{\pi }{5} \end{array} \right.\left( {k \in Z} \right)\)

C. \(\left[ \begin{array}{l} x = \frac{\pi }{2} + k\pi \\ x = - \frac{\pi }{4} + k\frac{\pi }{2}\\ x = \frac{\pi }{{10}} + k\frac{\pi }{5} \end{array} \right.\left( {k \in Z} \right)\)

D. \(\left[ \begin{array}{l} x = \frac{\pi }{2} + k\pi \\ x = \frac{\pi }{4} + k\frac{\pi }{2}\\ x = - \frac{\pi }{{10}} + k\frac{\pi }{5} \end{array} \right.\left( {k \in Z} \right)\)