In the following alphabet series, one term is missing. Select the group of letters that best completes the series: DE, GI, KN, ?

Introduction / Context:
This question tests your ability to recognize patterns in an alphabet series. Instead of numbers, we use pairs of letters and look for a logical rule that connects consecutive terms. Such questions are very common in aptitude and competitive exams because they check both observation skills and comfort with alphabetical positions.

Given Data / Assumptions:

• Given letter groups: DE, GI, KN, ? • We assume a standard English alphabet with positions A = 1, B = 2, ..., Z = 26. • The pattern is consistent across all consecutive pairs. • Exactly one of the given options completes the sequence correctly.

Concept / Approach:
To solve alphabet series questions, a reliable approach is to convert each letter to its numerical position in the alphabet and then observe how these numbers change. We normally examine each position in the pair separately: the first letters form one number sequence, and the second letters form another. Often the pattern involves adding or subtracting a fixed value, or increasing the difference step by step.

Step-by-Step Solution:
Step 1: Write numerical positions for each letter pair. DE = (D = 4, E = 5) GI = (G = 7, I = 9) KN = (K = 11, N = 14) Step 2: Look at the first letters: D (4), G (7), K (11). From 4 to 7 we add 3. From 7 to 11 we add 4. The increment itself increases by 1. Step 3: Continue the same pattern. The next jump for the first letter will be +5: 11 + 5 = 16, which is P. Step 4: Now consider the second letters: E (5), I (9), N (14). From 5 to 9 we add 4. From 9 to 14 we add 5. Again, the increment increases by 1. Step 5: Continue with +6 for the second letter: 14 + 6 = 20, which is T. Step 6: Therefore the missing term is PT.

Verification / Alternative check:
We can quickly verify by recomputing the pattern. First letters: 4, 7, 11, 16 correspond to D, G, K, P with increments +3, +4, +5. Second letters: 5, 9, 14, 20 correspond to E, I, N, T with increments +4, +5, +6. Both positions follow a smooth and consistent rule where the step size increases by 1 each time. This confirms that PT is the unique and correct completion of the series.

Why Other Options Are Wrong:
• PS: First letter P fits, but S corresponds to 19, not the required 20. The second letter pattern breaks. • PR: The first letter P is correct, but R corresponds to 18 and does not match the required +6 increment from N. • TP: Both letters break the established pattern. T would imply a different jump from K, and P does not match the second letter sequence.

Common Pitfalls:
Many learners only look at the overall feel of the letters and guess based on familiarity, without checking numeric positions. Another common mistake is to mix the patterns of the first and second letters instead of treating them as two separate sequences. Some candidates also assume a constant difference, while here the difference itself changes step by step. Carefully tracking each progression avoids such errors.

Final Answer:
The missing term that correctly completes the alphabet series is PT.