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If ""^nCr denotes the number of combinat...

If `""^nC_r` denotes the number of combinations of n things taken r at a time, then the expression `""^nC_(r+1)+""^nC_(r-1)+ 2xx""^nC_r` equals :

A

`""^(n+2)C_(r+1)`

B

`""^(n+1)C_(r)`

C

`""^(n+1)C_(r+1)`

D

`""^(n+2)C_(r)`.

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