问题
单项选择题
A company that ships boxes to a total of 12 distribution centers uses color coding to identify each center. If either a single color or a pair of two different colors is chosen to represent each center and if each center is uniquely represented by that choice of one or two colors, what is the minimum number of colors needed for the coding ？（） (Assume that the order of the colors in a pair does not matter.)
A.4
B.5
C.6
D.12
E.24
答案
参考答案：B
解析：
设最少需要用n种颜色，则n种颜色可表示的分配中心的数目为
，根据题意可得：
考虑到n只能取正整数，可解得n的最小值为5。