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? Choose the correct choice from the following options: A) 4 B) 5 C) 6 D) 7 E) 8
I think the order matters so I'm going w/B. I reasoned this one out.   Does "a pair of distinct letters written in alphabetical order" mean anything significant?   1 2 3 4 5 6 7 8 9 10 11 12   A 5 C D E AA A5 AC AD AE 5A 55
<result>B</result>
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?