The expression $\frac{{\cos 6x + 6\cos 4x + 15\cos 2x + 10}}{{\cos 5x + 5\cos 3x + 10\cos x}}$ is equal to

  • A

    $\cos 2x$

  • B

    $2\cos x$

  • C

    ${\cos ^2}x$

  • D

    $1 + \cos x$

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