In the alphabet pair series KV, LU, MT, ?, which of the following pairs of letters should replace the question mark to continue the pattern based on the positions of letters in the English alphabet?

Introduction / Context:
This question features a two letter alphabet series: KV, LU, MT, ?, and we must determine the next pair of letters. Each term is made of two capital letters, and the sequence is governed by a systematic change in their positions. This type of problem tests recognition of opposing movements in the alphabet, a common theme in reasoning questions involving letter pairs.

Given Data / Assumptions:

• Known pairs: KV, LU, MT.
• Each pair consists of two letters.
• The first letters form one sequence, and the second letters form another.
• Options: NS, OS, OU, SN.

Concept / Approach:
The main idea is to convert each letter into its numeric position and look at changes separately for the first and second positions. Very often in such series, one letter sequence increases while the other decreases. Once we identify the step size for both sequences, we can extend them to find the missing pair that continues the pattern exactly.

Step-by-Step Solution:
Step 1: Convert the first letters: K(11), L(12), M(13). These values increase by 1 from term to term.Step 2: The next first letter after M(13), following the same pattern, should be 14, which is N.Step 3: Convert the second letters: V(22), U(21), T(20). These values decrease by 1 from term to term.Step 4: The next second letter after T(20), using the same pattern, should be 19, which is S.Step 5: Combining these results, the missing pair of letters is NS.

Verification / Alternative check:
The complete sequence of pairs becomes KV (11, 22), LU (12, 21), MT (13, 20), NS (14, 19). The first letter position advances 11, 12, 13, 14, and the second letter position retreats 22, 21, 20, 19. This confirms that NS fits perfectly into both arithmetic progressions and is the correct continuation.

Why Other Options Are Wrong:
OS would have the first letter O(15), which jumps by 2 instead of 1 from M(13). OU would keep the second letter increasing relative to T, violating the decreasing pattern. SN reverses the order of N and S and does not follow the systematic increase and decrease in their respective positions. Therefore, they cannot complete the series correctly.

Common Pitfalls:
Many learners treat the pair as a whole and do not separate the two positions. Others may remember roughly where letters are in the alphabet, but miscount exact positions. To avoid such mistakes, always analyse each position independently and verify that both parts of the pair adhere to the same symmetry or arithmetic rule.

Final Answer:
The pair that correctly continues the series is NS.