Let $x_{i} (1 \leq i \leq 10)$ be ten observations of a random variable $X$. If $\sum_{i=1}^{10} (x_{i} - p) = 3$ and $\sum_{i=1}^{10} (x_{i} - p)^{2} = 9$,where $0 \neq p \in R$,then the standard deviation of these observations is:

  • A
    $\sqrt{\frac{3}{5}}$
  • B
    $\frac{7}{10}$
  • C
    $\frac{9}{10}$
  • D
    $\frac{4}{5}$

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