If the coefficients of $x^7$ in $\left( ax ^2+\frac{1}{2 bx }\right)^{11}$ and $x ^{-7}$ in $\left(a x-\frac{1}{3 b x^2}\right)^{11}$ are equal, then

  • [JEE MAIN 2023]
  • A

    $64 ab =243$

  • B

    $729 ab =32$

  • C

    $243 ab =64$

  • D

    $32 ab =729$

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