If $0 \le x < 2\pi $ , then the number of real values of $x,$ which satisfy the equation  $\cos x + \cos 2x + \cos 3x + \cos 4x = 0$ is  . .  .

  • [JEE MAIN 2016]
  • A

    $7$

  • B

    $9$

  • C

    $3$

  • D

    $5$

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