The mean and $S.D.$ of $1, 2, 3, 4, 5, 6$ is

  • A

    $\frac{7}{2},\,\sqrt {\frac{{35}}{{12}}} $

  • B

    $3, 3$

  • C

    $\frac{7}{2},\,\sqrt 3 $

  • D

    $3,\,\frac{{35}}{{12}}$

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