ywilfred wrote:

A

B

AB

C

BC

AC

D

AD

BD

CD

E

So 5 letters needed

This question is pissing me off because its not designed well...

"or a pair of distinct letters written in alphabetical order."

That clearly means that AD, AC, cannot be used.... these are not in alphabetical order.

I got 7.

A, B, C, D, E, F, G, AB, BC, CD, DE, EF

Obviously the official answer is 5 but can someone please explain to me whe

"a pair of distinct letters written in alphabetical order" is not nullifying AC or AD.... AC is not in alphabetical order.