Let $x_1,x_2,.........,x_{100}$ are $100$ observations such that  $\sum {{x_i} = 0,\,\sum\limits_{1 \leqslant i \leqslant j \leqslant 100} {\left| {{x_i}{x_j}} \right|} }  = 80000\,\& $ mean deviation from their mean is $5,$ then their standard deviation, is-

  • A

    $10$

  • B

    $30$

  • C

    $40$

  • D

    $50$

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