In the alphabet series AZ, GT, MN, ?, YB, one term is missing. Choose the pair of letters that correctly completes the series.

Introduction / Context:
We are given an alphabet series with two letter groups: AZ, GT, MN, ?, YB. The task is to identify which pair of letters fits in place of the question mark. These series usually have separate patterns for the first letters and the second letters, often involving fixed jumps through the alphabet.

Given Data / Assumptions:

• Series: AZ, GT, MN, ?, YB.
• Each term is a pair of capital letters.
• We examine the first letters separately from the second letters.

Concept / Approach:
For such alphabet pairs, treat the first letters as one sequence and the second letters as another. Look at alphabetical positions (A = 1, B = 2, ..., Z = 26) and identify the step size. These step sizes may be constant or follow a simple pattern like plus or minus a fixed number of positions.

Step-by-Step Solution:
1. Write out the first letters of each pair: A, G, M, ?, Y. 2. Convert these to positions: A(1), G(7), M(13), ?, Y(25). 3. Differences: 1 to 7 is +6, 7 to 13 is +6, 13 to ? should be +6, and then from that result to 25 should again be +6. 4. So the sequence of first letters is increasing by 6 each time. 5. From M(13), add 6 to get 19, which corresponds to S. So the first letter of the missing pair is S. 6. Now write the second letters: Z, T, N, ?, B. 7. Convert to positions: Z(26), T(20), N(14), ?, B(2). 8. Differences: 26 to 20 is -6, 20 to 14 is -6, so each step moves 6 letters backward. 9. From N(14), subtract 6 to get 8, which is H. From H(8), subtract 6 we get B(2), which matches the last term. 10. Therefore the missing pair is S (first letter) and H (second letter), forming SH.

Verification / Alternative check:
Rebuild the full series with the missing term as SH: First letters: A(1), G(7), M(13), S(19), Y(25) move +6 each time. Second letters: Z(26), T(20), N(14), H(8), B(2) move -6 each time. Both sequences are perfectly consistent, so SH is correct.

Why Other Options Are Wrong:

• TS: First letter T(20) does not continue the +6 pattern from M(13), which demands S(19). It also breaks the symmetric backward movement in the second letters.
• KF: K(11) does not fit the first letter pattern, and F(6) breaks the second letter pattern.
• RX: R(18) is not 6 positions after M(13), and X(24) is not 6 positions before B(2) when we move cyclically in a consistent way.

Common Pitfalls:
A common mistake is to focus on the visual shapes of the letters rather than converting them into numeric positions. Without computing these positions, the constant step of +6 and -6 is easy to miss. Another error is to assume the same direction for both first and second letters, whereas here they move in opposite directions, creating a symmetric pattern.

Final Answer:
The pair of letters that correctly completes the series is SH.