If $\alpha $ is a root of $25{\cos ^2}\theta + 5\cos \theta - 12 = 0$, $\pi /2 < \alpha < \pi $, then $\sin 2\alpha $ is equal to

  • A

    $24/25$

  • B

    $ - 24/25$

  • C

    $13/18$

  • D

    $ - 13/18$

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