The middle term in the expansion of ${\left( {3x - \frac{{{x^3}}}{6}} \right)^9}$ are :-

  • A

    $ - \frac{{21}}{{16}}{x^{19}},\frac{{189}}{9}{x^{17}}$

  • B

    $\frac{{21}}{{16}}{x^{19}},-\frac{{189}}{8}{x^{17}}$

  • C

    $\frac{{201}}{{18}}{x^{17}},\frac{{21}}{{16}}{x^{18}}$

  • D

    none of these

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