If $\sum\limits_{r = 0}^{25} {\left\{ {^{50}{C_r}.{\,^{50 - r}}{C_{25 - r}}} \right\} = K\left( {^{50}{C_{25}}} \right)} $, then $K$ is equal to

  • [JEE MAIN 2019]
  • A

    $(25)^2$

  • B

    $2^{25} -1$

  • C

    $2^{24}$

  • D

    $2^{25}$

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