A series of two letter terms is given with one term missing. Choose the correct alternative from the given options that will complete the series BE, HK, NQ, ?

Introduction / Context:
This is a two letter alphabet series problem where both the first and second letters follow a pattern as we move from one term to the next. The question tests the ability to recognise consistent jumps in letter positions and extend that pattern for the missing term.

Given Data / Assumptions:

• The given series is BE, HK, NQ, ?
• Each term consists of two uppercase letters.
• We use alphabetical positions A = 1 to Z = 26.
• The same pattern is assumed to apply for the entire series.

Concept / Approach:
As with many letter pair series, we treat the first letters as one sequence and the second letters as another. We then check the difference between consecutive letters in each sequence. Once the increment is identified, we apply it to get the next letters of the missing pair.

Step-by-Step Solution:
Step 1: Consider the first letters: B, H, N. Step 2: Their positions are B = 2, H = 8, N = 14. Step 3: From 2 to 8 the difference is plus 6. From 8 to 14 the difference is also plus 6. So we add 6 again to 14. Step 4: 14 plus 6 equals 20, which corresponds to T. Hence, the first letter of the missing pair is T. Step 5: Now look at the second letters: E, K, Q. Step 6: Their positions are E = 5, K = 11, Q = 17. Step 7: From 5 to 11 the difference is plus 6, and from 11 to 17 it is plus 6 again. So we add 6 to 17. Step 8: 17 plus 6 equals 23, which corresponds to W. So the second letter of the missing pair is W. Step 9: Therefore, the missing term is TW.

Verification / Alternative check:
Observe that each pair consists of letters that are 3 places apart, but more importantly the starting letters themselves are spaced by plus 6 and the ending letters are also spaced by plus 6. Continuing this pattern leads uniquely to TW. No other option supports the plus 6 progression in both positions.

Why Other Options Are Wrong:
ST, TU, and TS all begin with T but their second letters do not arise from adding 6 to Q. ST would correspond to 19 instead of 23, TU to 21, and TS to 19. None of these match the required step. The none of these option is incorrect because TW clearly satisfies the consistent plus 6 pattern.

Common Pitfalls:
Often, students notice that letters seem to move towards the end of the alphabet and choose pairs like TU based on proximity. Others may ignore the exact numerical step and rely only on visual closeness. Writing down exact positions and performing the arithmetic eliminates such guesswork.

Final Answer:
The correct pair that completes the series is TW.