In this letter pair analogy, “TU is to MN as JK is to ______”. Choose the pair of letters that completes the analogy by following the same backward shift in the alphabet for both letters.

Introduction / Context:
This analogy involves two letter pairs where the letters are shifted backward in the alphabet by the same number of positions. The pair TU : MN shows that each letter in TU is transformed into the corresponding letter in MN using a constant backward shift. Our job is to determine that shift and then apply it to the pair JK to find its matching pair from the options. These questions test accuracy in working with sequential letter positions.

Given Data / Assumptions:

• First pair mapping: TU → MN. • Second pair mapping: JK → ? • Options: CD, RS, TM, KL. • Alphabet positions: A = 1, B = 2, ..., Z = 26.

Concept / Approach:
We examine the mapping from T to M and from U to N in terms of their position numbers. If T moves backward by a fixed number of positions to become M, and U moves backward by the same number to become N, we have a consistent rule. Once that backward shift is known, we apply it to J and K. The correct answer will be the option that matches the resulting letters exactly in both positions.

Step-by-Step Solution:
Step 1: Convert TU to numeric positions. T = 20, U = 21. Step 2: Convert MN to numeric positions. M = 13, N = 14. Step 3: Compute the shifts. 20 → 13 is a shift of −7. 21 → 14 is also a shift of −7. Thus, each letter is moved backward by 7 positions. Step 4: Apply the same rule to JK. J = 10, K = 11. 10 − 7 = 3 → C. 11 − 7 = 4 → D. So JK maps to CD.

Verification / Alternative check:
We can verify by applying the reverse shift of +7. Starting from MN, adding 7 returns T and U: M (13) + 7 = T (20), N (14) + 7 = U (21). Similarly, starting from CD, adding 7 gives J and K: C (3) + 7 = J (10), D (4) + 7 = K (11). This shows that the backward shift of 7 is consistent and symmetrical for both pairs, confirming the pattern.

Why Other Options Are Wrong:
• RS: These letters are near TU rather than 7 positions behind JK, and they do not match the computed shifts. • TM: Here the letters do not result from subtracting 7 from J and K. • KL: Actually follows J and K in the alphabet, representing a forward shift, which contradicts the backward pattern observed in TU → MN.

Common Pitfalls:
Some candidates may incorrectly assume a forward shift or confuse the direction of the mapping, especially when reading the pair as MN : TU instead of TU : MN. Always note which side is given as the starting point in the analogy and compute the shift from that side to the other. Converting letters to numbers and doing simple subtraction is the most reliable method for these patterns.

Final Answer:
The letter pair that correctly completes the analogy is CD.