In this letter pair reasoning question, select the pair of letters that does not follow the same positional difference pattern as the others: PE, MV, GP and DM.

Introduction / Context:
Odd one out questions using letter pairs often hide a fixed difference in alphabetical positions between the first and second letter. In this problem, you are given four such pairs and asked to identify which pair does not share the same difference. These questions check your familiarity with alphabetical positions and your ability to spot simple numeric patterns within letters.

Given Data / Assumptions:

• The letter pairs are PE, MV, GP and DM.
• We assign positions to letters in the English alphabet: A = 1, B = 2, C = 3, and so on.
• We find the difference between the position of the second letter and the first letter in each pair.

Concept / Approach:
A standard approach is to convert each letter into its position and calculate the difference. If three pairs show the same difference (for example plus 9), and one pair shows a different value, then that different pair is the odd one out. This method transforms a verbal pattern into a simple arithmetic pattern on numbers.

Step-by-Step Solution:
Step 1: For PE, P is the 16th letter and E is the 5th letter. The difference is 16 - 5 = 11 in absolute value. Step 2: For MV, M is the 13th letter and V is the 22nd letter. The difference is 22 - 13 = 9. Step 3: For GP, G is the 7th letter and P is the 16th letter. The difference is 16 - 7 = 9. Step 4: For DM, D is the 4th letter and M is the 13th letter. The difference is 13 - 4 = 9. Step 5: Thus three pairs (MV, GP and DM) have a difference of 9 between first and second letter, while PE has a difference of 11. Hence PE is the odd one out.

Verification / Alternative check:
We can cross verify by noting that moving 9 steps forward from M gives V, from G gives P, and from D gives M. However, moving 9 steps from P would not give E, and moving 11 steps back from P gives E. The consistent pattern for three pairs is a fixed jump of 9 alphabet positions, which PE breaks. This confirms that PE is the unique non matching pair.

Why Other Options Are Wrong:
MV is wrong as the odd one out because the letters are separated by 9 positions, matching the main pattern. GP is wrong as the odd one out because it also shows a difference of 9 and fits the same rule. DM is wrong as the odd one out because it continues the same relationship with a difference of 9.

Common Pitfalls:
Students sometimes look for forward or backward order alone and ignore the exact numeric difference. Others may calculate position differences incorrectly by miscounting letters. A good way to avoid errors is to write down positions or at least check them quickly in your mind using known reference points such as A = 1, M = 13 and Z = 26. Once the differences are computed carefully, the pattern becomes obvious.

Final Answer:
The only pair that does not have a difference of 9 between the letters, and therefore the odd one out, is PE.