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

  • A
    $\frac{(2n)!}{(n-r)!(n+r)!}$
  • B
    $\frac{n!}{(n-r)!(n+r)!}$
  • C
    $\frac{n!}{(n-r)!}$
  • D
    None of these

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