Hint #1
Don’t look for relationships between every letter.
Hint #2
Try looking for relationships between every other letter.
Hint #3
Let’s look at every odd letter:
A, B, C, D, ?
A, B, C, D, ?
Answer
EE
The odd positions are letters sequential by one in ascending order.
The even positions are vowels in descending order, starting with A and wrapping to U. You can also look at it as the five vowels.
