If ${a_k} = \frac{1}{{k(k + 1)}},$ for $k = 1,\,2,\,3,\,4,.....,\,n$, then ${\left( {\sum\limits_{k = 1}^n {{a_k}} } \right)^2} = $

  • A

    $\left( {\frac{n}{{n + 1}}} \right)$

  • B

    ${\left( {\frac{n}{{n + 1}}} \right)^2}$

  • C

    ${\left( {\frac{n}{{n + 1}}} \right)^4}$

  • D

    ${\left( {\frac{n}{{n + 1}}} \right)^6}$

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