Which of the following is not the number of ways of selecting `n` objects from `2n` objects of which `n` objects are identical

Options

A. a) `2^(n)`
B. b) `("^(2n+1)C_(0)+^(2n+1)C_(1)+...+^(2n+1)C_(n))^(1//2)`
C. c) the number of possible subsets `{a_(1),a_(2),….,a_(n)}`
D. d) None of these

Answer

D

Explanation

`(d)` We can take `0` indentical and `n` distinct , `1` identical and `n-1` distinct , `2` identical and `n-2` distinct and so on…
`:.` Total no. of solutions `=sum_(r=0)^(n).^(n)C_(r )=2^(n)`
No. of possible subsets of a set containing `n` elements is `2^(n)` and `.^(2n+1)C_(0)+^(2n+1)C_(1)+^(2n+1)C_(2)+...+^(2n+1)C_(n)=2^(2n)`