In the following letter series c_e_cd_f_d_f, which one set of letters, when sequentially placed in the blanks, will complete the series in a consistent alphabetical pattern?

Introduction / Context:
This verbal reasoning question is about completing a letter series by inserting the correct sequence of letters into blanks. The goal is to identify the underlying pattern and choose the option that makes the entire sequence consistent. Such questions are common in aptitude tests and measure pattern recognition and attention to order in alphabets.

Given Data / Assumptions:

• Given series with blanks: c_e_cd_f_d_f.
• There are five blanks to be filled.
• Each option gives a five letter sequence to place in the blanks from left to right.
• Exactly one option should make the complete sequence follow a simple pattern.

Concept / Approach:
First, mark the positions of the blanks and then test each candidate option by inserting its letters sequentially. After filling the blanks, inspect the resulting sequence for a simple, repeating alphabetic pattern. A neat repetition is a strong indicator of the correct choice, especially in letter series where consecutive letters such as c, d, e and f frequently appear.

Step-by-Step Solution:
Step 1: The pattern is c _ e _ c d _ f _ d _ f, with blanks at positions 2, 4, 7, 9 and 11.Step 2: Insert the option "dfece" in order: position 2 = d, 4 = f, 7 = e, 9 = c, 11 = e.Step 3: The completed series becomes: c d e f c d e f c d e f.Step 4: Now we clearly see a perfectly repeating pattern: c d e f repeated three times in succession.Step 5: None of the other options produce such a clean and regular repetition.

Verification / Alternative check:
If we try the other answer choices, they create irregular strings that do not follow a simple repetition of four consecutive letters. Only with "dfece" do we get c d e f c d e f c d e f, which is a very natural and symmetric pattern in the alphabet. This strongly confirms that option "dfece" is the intended completion.

Why Other Options Are Wrong:

• "dfcec", "cfede", "cdfed" and "cedfd" all break the c d e f repetition at some point.
• They produce sequences where letters do not progress uniformly through the alphabet.

Common Pitfalls:
Some candidates focus only on local segments and miss the global pattern of repetition. Others may try to force a complex rule when a simple cyclic pattern is present. In letter series questions, always look for repeated blocks and natural alphabet sequences first, as they are usually the intended structure.

Final Answer:
The sequence is completed as c d e f c d e f c d e f, so the correct set of letters is "dfece".