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
ANS=B
他說code是包含一個字母 或 兩個不同字母writing in alphabetical order,後半段這句話是什麼意思?
因為我的答案是A,應該是題目沒看懂。
是說AB 不能寫成BA嗎?