If $\sin \theta = \frac{{ - 4}}{5}$ and $\theta $ lies in the third quadrant, then $\cos \frac{\theta }{2} = $

  • A

    $\frac{1}{{\sqrt 5 }}$

  • B

    $ - \frac{1}{{\sqrt 5 }}$

  • C

    $\sqrt {\frac{2}{5}} $

  • D

    $ - \sqrt {\frac{2}{5}} $

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