A series of three-letter letter-blocks is given with one term missing. The blocks use consecutive English letters with a fixed jump between starting letters and wrap around the alphabet. Select the correct alternative from the given options that will complete the series: FGH, NOP, VWX, ?

Introduction / Context:
This logical sequence question involves groups of three consecutive letters from the English alphabet: FGH, NOP, VWX and a missing fourth group. The pattern concerns how the starting letter of each block changes from term to term, including a wrap-around at the end of the alphabet. You must identify this pattern and then choose the letter-block that continues it correctly. Such questions assess your ability to recognise numerical patterns hidden in letter sequences.

Given Data / Assumptions:

• Given series: FGH, NOP, VWX, ?
• Options: FGH, DEF, EFG, FGH (two identical FGH options are provided).
• Each term consists of three consecutive letters in alphabetical order.
• The starting letter of each term seems to jump forward through the alphabet by a fixed number of positions.
• When the sequence passes beyond Z, it wraps around to the beginning of the alphabet.

Concept / Approach:
The first step is to convert each starting letter into its alphabetical position: A=1, B=2, and so on, up to Z=26. We then examine how these starting positions change from one term to the next. If the difference is constant, we are dealing with an arithmetic progression in letter positions. Because the alphabet is finite, when we add a value that exceeds 26 we take the result modulo 26 (wrapping back to A, B, C and so on). Once the next starting position is found, the missing term is simply three consecutive letters beginning from that letter.

Step-by-Step Solution:
Step 1: Identify the starting letters of each term: F, N and V. Step 2: Convert these letters to their alphabetical positions: F = 6, N = 14, V = 22. Step 3: Find the difference between consecutive starting positions: 14 − 6 = 8 and 22 − 14 = 8. Thus the sequence of starting letters increases by 8 positions each time. Step 4: To find the next starting letter, add 8 to the last starting position: 22 + 8 = 30. Because the alphabet has 26 letters, wrap around by subtracting 26: 30 − 26 = 4, which corresponds to the letter D. Step 5: Therefore, the next block in the sequence must start with D and contain the next two letters E and F, giving the letter-block DEF. Step 6: Among the options, DEF is present and matches the required pattern, so DEF is the correct missing term.

Verification / Alternative check:
To verify, you can list the sequence with the numeric positions of the starting letters: 6 (F), 14 (N), 22 (V), 4 (D) after wrap-around. These form an arithmetic progression with common difference +8 modulo 26. Each term is followed by the next two letters, so the blocks are FGH, NOP, VWX and DEF. None of the repeated FGH options introduces a new starting letter or maintains the +8 pattern, and EFG does not fit the computed starting position of 4. This confirms that only DEF satisfies the pattern.

Why Other Options Are Wrong:
FGH, whether appearing once or twice, simply repeats the first term and does not follow the observed jump of +8 positions from one block to the next. EFG would correspond to starting from E (position 5), which does not match the required starting position of D (position 4) derived from adding 8 to 22 modulo 26. Hence these alternatives do not continue the established pattern of starting positions and cannot be correct.

Common Pitfalls:
Some candidates may focus only on the visible groups and attempt to guess based on visual similarity, overlooking the arithmetic pattern in the starting letters. Others may forget to wrap around after Z and incorrectly compute the next starting letter. To avoid mistakes, always convert letters to numerical positions, check the differences between them, apply modular arithmetic if necessary and then convert back to letters. This systematic approach makes it much easier to handle alphabet-based sequences correctly.

Final Answer:
Using a constant step of 8 positions in the alphabet and wrapping around after Z, the next starting letter is D and the corresponding three-letter block is DEF. Therefore DEF is the correct answer.