Problem Solving
试题详情
题目：
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 alphabetic 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?
选项:
A、4
B、5
C、6
D、7
E、8
答案:
B
