Choose the odd one out.

PQs
AtB
SiM
mnZ E. DfE

The answer is D. mnZ.

In each of the other options, the first two letters are the first two letters of the alphabet, and the last two letters are the last two letters of the alphabet. In D. mnZ, the first two letters are not the first two letters of the alphabet, and the last two letters are not the last two letters of the alphabet.