If $x\cos \theta = y\cos \,\left( {\theta + \frac{{2\pi }}{3}} \right) = z\cos \,\left( {\theta + \frac{{4\pi }}{3}} \right),$ then the value of $\frac{1}{x} + \frac{1}{y} + \frac{1}{z}$ is equal to

  • [IIT 1984]
  • A

    $1$

  • B

    $2$

  • C

    $0$

  • D

    $3\,\,\cos \theta $

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