A series of three letter groups is given: ACE, FHJ, KMO, ? Choose the group of letters that correctly continues this pattern in the English alphabet.

Introduction / Context:
This problem is a classical alphabet series question. We are given several groups of three letters and we must recognise the underlying pattern in their positions in the English alphabet. Once the pattern is discovered, we can extend it to find the missing group. Such questions test a candidate ability to work with letter positions, constant differences, and simple progression rules rather than language meaning.

Given Data / Assumptions:

• Given groups: ACE, FHJ, KMO, ? • Options: QRS, PRT, PRU, QRV • Alphabet positions: A 1, B 2, C 3, D 4, E 5, F 6, G 7, H 8, I 9, J 10, K 11, L 12, M 13, N 14, O 15, P 16, Q 17, R 18, S 19, T 20, and so on. • Assumption: The same pattern of jumps or differences should connect all groups consistently.

Concept / Approach:
We examine the positions of letters in each group separately for the first, second, and third letters. Often, alphabet series use a constant step size or a repeated pattern of steps for each column. If we can determine a fixed difference between successive groups for each column, we can apply that same difference to the last known group KMO to find the missing one. Checking all columns also helps confirm that we have discovered a reliable pattern rather than a coincidence.

Step-by-Step Solution:
Step 1: First letters: A, F, K. Positions are 1, 6, and 11. The difference is +5 each time (1 to 6, 6 to 11). So the next first letter is 11 + 5 = 16, which is P. Step 2: Second letters: C, H, M. Positions are 3, 8, and 13. Again, the difference is +5 each time (3 to 8, 8 to 13). So the next second letter is 13 + 5 = 18, which is R. Step 3: Third letters: E, J, O. Positions are 5, 10, and 15. The same pattern holds: +5 each time (5 to 10, 10 to 15). So the next third letter is 15 + 5 = 20, which is T. Step 4: Therefore the next group is formed by letters P, R, and T, so the missing term is PRT.

Verification / Alternative check:
To verify, we can write the series with positions underneath: ACE is (1,3,5), FHJ is (6,8,10), and KMO is (11,13,15). Each coordinate increases by 5 when we go from one group to the next. Extending this pattern gives (16,18,20), which corresponds exactly to PRT. None of the other options matches the pattern of plus five for all three letters, which confirms that PRT is the only consistent continuation of the sequence.

Why Other Options Are Wrong:
QRS has positions (17,18,19), which does not maintain the constant +5 step from the previous group in any column. PRU has letters P, R, U with positions (16,18,21); the third letter position 21 breaks the +5 pattern that predicts 20. QRV gives positions (17,18,22); again the jumps from KMO are not all +5, so the pattern fails.

Common Pitfalls:
A frequent mistake is to look only at the first letters and find a partial pattern, then guess without checking the other two letters. Another common error is to misremember letter positions beyond N, leading to small counting mistakes. Writing the alphabet with positions on paper and carefully checking the differences column wise makes the logic clear and reduces careless errors.

Final Answer:
The group that correctly continues the series ACE, FHJ, KMO is PRT.