Choose the odd one out.

Let's analyze the alphabetical relationship between the letters in each option:
* KL: $K$ and $L$ are consecutive letters in alphabetical order ($11$ and $12$).
* QR: $Q$ and $R$ are consecutive letters in alphabetical order ($17$ and $18$).
* AZ: $A$ and $Z$ are opposite letters in the alphabet ($A$ is 1st from the beginning, $Z$ is 1st from the end). They are not consecutive.
* FG: $F$ and $G$ are consecutive letters in alphabetical order ($6$ and $7$).

All options except AZ consist of pairs of consecutive letters. Therefore, AZ is the odd one out.