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If ""^(n)C( r ):""^(n)C(r+1):""^(n)C(r+2...

If `""^(n)C_( r ):""^(n)C_(r+1):""^(n)C_(r+2)=1:2:3`, then r is equal to

A

5

B

4

C

3

D

0

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The correct Answer is:
B
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""^(n)C_(r+1)+^(n)C_(r-1)+2.""^(n)C_(r)=

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