${C_0}{C_r} + {C_1}{C_{r + 1}} + {C_2}{C_{r + 2}} + .... + {C_{n - r}}{C_n}$=

  • A

    $\frac{{(2n)!}}{{(n - r)\,!\,(n + r)!}}$

  • B

    $\frac{{n!}}{{( - r)!(n + r)!}}$

  • C

    $\frac{{n!}}{{(n - r)!}}$

  • D

    None of these

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