Cathy likes to wear 2 ribbons, each a different color. If she has 6 ribbons each of a different color, how many combinations of 2 different-colored ribbons can she select to wear?
(A) 3
(B) 6
(C) 12
(D) 15
(E) 36
SAT I 每日一问：2012年6月29日
2012-07-06 14:37
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