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If n is positive integer, sum(r = 1)^(n...

If n is positive integer, `sum_(r = 1)^(n) (.^(n)C_(r))^(2) =`

A

zero

B

`.^(n)C_(n//2)`

C

`((2n)!)/(n!)`

D

`((2n)!)/((n!)^(2)) - 1`

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