In the alphabet series GHI, ?, TUV, BCD, which group of three letters should fill the missing place so that the overall pattern is maintained?

Introduction / Context:
This question involves a non-linear alphabet series where the triplets GHI, ?, TUV, BCD appear in sequence. The missing triplet must be chosen so that the pattern in the starting letters is consistent. Although the terms look widely separated, there is a simple rule governing the movement of the first letters through the alphabet. Recognising this movement allows us to identify the correct middle term.

Given Data / Assumptions:

• Known triplets: GHI, ?, TUV, BCD.• Each triplet consists of three consecutive letters in ascending order (for example, G, H, I).• Only the starting letter of each triplet is essential for determining the pattern.• The alphabet positions A=1, B=2, ..., Z=26 will be used.

Concept / Approach:
We represent the first letters numerically and search for a pattern in the jumps between them. Let the first letters of the four positions be G, X, T and B, where X is unknown. By examining differences such as G to X, X to T and T to B, we can look for a systematic sequence of increments. An alternating growth in the jump sizes is a common feature in such problems.

Step-by-Step Solution:
Positions of first letters: G=7, T=20, B=2 (or 28 in cyclic form).We hypothesise that the increments between consecutive first letters increase by one each step.Assume the pattern of increments is +6, +7, +8.Starting with G (7), adding 6 gives 13, which is M.Adding 7 to M (13) gives 20, which is T, matching the given third triplet TUV.Adding 8 to T (20) gives 28, and 28 − 26 = 2, which corresponds to B, matching the fourth triplet BCD.Therefore, the missing first letter must be M, and the corresponding ascending triplet is MNO.

Verification / Alternative check:
By substituting MNO in the second position, the full series of first letters becomes G (7), M (13), T (20), B (2 or 28). The increments are +6, +7 and +8, which is a smooth and logical progression. Each triplet, including MNO, maintains the internal ascending pattern of three consecutive letters, reinforcing the consistency of the solution. No other option yields this exact combination of a steadily increasing increment plus a correct consecutive-letter triplet.

Why Other Options Are Wrong:
ONP, QRS and CDE all start from letters that do not satisfy the +6, +7, +8 increment pattern when paired with G, T and B. For instance, Q (17) would create a jump of +10 from G, which is inconsistent with later changes. C (3) does not generate a smooth set of incremental differences either. Therefore, these options must be rejected in favour of MNO, which fits the numeric pattern perfectly.

Common Pitfalls:
Students may be tempted to look for a direct alphabetical sequence across all triplets or assume equal jumps between starting letters. Another pitfall is ignoring the cyclic nature of the alphabet when it wraps from Z back to A. Considering these aspects, and explicitly calculating positions and differences, makes the logic behind MNO clear and avoids random guessing.

Final Answer:
MNO