A bag contains `n`
white and `n`
red balls. Pairs of balls are drawn without replacement until the bag is
empty. Show that the probability that each pair consists of one white and one
red ball is `(2^n)/(^(2n)C_n)`
A. `1//^(2n)C_(n)`
B. `2n//^(2n)C_(n)`
C. `2n//n!`
D. `2n//(2n!)`