A mixed-case alphabet series is given with one term missing. The sequence uses consecutive English letters with an alternating upper and lower case pattern, and each term is longer than the previous one. Choose the correct alternative from the given options that will complete the series: AbC, dEfG, hIjKl, MnOpQr, ?

Introduction / Context:
This is a logical sequence of letters question that combines two ideas: the natural alphabetical order of English letters and a deliberate pattern of upper and lower case usage. The terms AbC, dEfG, hIjKl and MnOpQr look unusual at first glance, but they conceal a regular structure. Your job is to identify that structure and then pick the option that continues it. Such problems test detailed pattern recognition rather than vocabulary or grammar knowledge.

Given Data / Assumptions:

• Given sequence: AbC, dEfG, hIjKl, MnOpQr, ?
• Options: StUvWxY, StUvWx, StUvWxYZ, sTuVwXy.
• All terms are built from consecutive letters of the English alphabet.
• Letter case (upper or lower) is meaningful and must follow a consistent internal pattern within each term.
• The length of each term appears to be changing in a controlled way.

Concept / Approach:
To decode this series, we should examine three aspects: which letters are used, how many letters are in each term and how the upper/lower case alternation behaves. First, we observe the alphabetical run covered by each term, then see how the starting letter for each new term is chosen. Next, we count the letters to see if the term length is following a simple progression. Finally, we confirm that the pattern of upper and lower case alternates consistently within each term and is compatible with the proposed next term.

Step-by-Step Solution:
Step 1: Identify the letters in each term. AbC uses A, B, C; dEfG uses D, E, F, G; hIjKl uses H, I, J, K, L; MnOpQr uses M, N, O, P, Q, R. Step 2: Notice that these sets of letters are continuous segments of the alphabet: A–C, D–G, H–L and M–R. The gaps between starting letters are +3, +4 and +5 positions respectively, so the next start should be 6 positions after M (13th letter), that is S (19th letter). Step 3: Count the letters per term: AbC has 3 letters, dEfG has 4, hIjKl has 5 and MnOpQr has 6. The length is increasing by one letter each time, so the next term must have 7 letters. Step 4: Continuing from S with 7 consecutive letters gives S, T, U, V, W, X, Y. Therefore the skeleton of the next term must be STUVWXY in that order. Step 5: Inside each term, letter case alternates upper, lower, upper, lower and so on, starting with uppercase in the first term, lowercase in the second, lowercase in the third and uppercase again in the fourth. For the fifth term to fit smoothly in the visual pattern, it is natural to start with uppercase S and then alternate case throughout, giving StUvWxY. Step 6: Among the options, only StUvWxY uses seven letters S to Y in order and alternates case correctly, so it must be the missing term.

Verification / Alternative check:
As a quick check, ignore case and list the raw letter blocks: ABC, DEFG, HIJKL, MNOPQR. The lengths form the sequence 3, 4, 5, 6, so the next block must have length 7. Continuing the alphabet after R produces S–Y exactly once, so STUVWXY is forced. Now restore the alternating case pattern. Trying each option, only StUvWxY matches both the required letters and the increasing length, confirming it as the only consistent continuation of the series.

Why Other Options Are Wrong:
StUvWx has only 6 letters, so it breaks the length pattern of 3, 4, 5, 6, 7. StUvWxYZ has 8 letters and also introduces Z, which goes beyond Y and disrupts the carefully controlled letter-block sizes. sTuVwXy has the correct alphabet segment and length but starts in lowercase and reverses the expected visual alternation when viewed against the earlier terms, making the overall sequence much less regular. Therefore none of these can be accepted as the intended next term.

Common Pitfalls:
Students often focus only on the case pattern and overlook the more fundamental alphabet and length structure, leading them to choose a visually appealing but incorrect option. Others notice the alphabet segments but forget to check that the number of letters increases by exactly one at each step. A careful approach is to analyse letters, length and case separately, then intersect the constraints. This method quickly eliminates wrong options and leads reliably to the correct answer.

Final Answer:
The next block must consist of seven consecutive letters from S to Y with alternating upper and lower case. The only option that satisfies all these conditions is StUvWxY, so that is the correct completion of the series.