请教GWD19-22

stevegt

Q22:

A researcher plans to identify each participant in a certain medical experiment with a code consisting of either a single letter or a pair of distinct letters written in alphabetical order. What is the least number of letters that can be used if there are 12 participants, and each participant is to receive a different code?

A. 4

B. 5

C. 6

D. 7

E. 8

stevegt

明白了。谢谢！！！！！

applebees

设共选出x个字母

x+C(x,2)>=12

当X为4时，只能区分十个人；当X为5时，可区分15个人

A，B，C，D ，E，AB，AC，AD，AE，BC，BD，BE，CD，CE，DE

the least number of letters 为5