In each of the following questions a letter-series is given, in which some letters are missing. The missing letters are given in the proper sequence as one of the alternatives. Choose the correct alternative: _ op _ mo _ n _ _ pnmop _

Introduction / Context:
This letter series question involves completing a string so that it becomes a repetition of a short block of letters. Candidates must determine which sequence of letters, when inserted into the blanks, produces a perfectly regular repeating pattern. The incomplete string is _ op _ mo _ n _ _ pnmop _.

Given Data / Assumptions:
- Incomplete series: _ o p _ m o _ n _ _ p n m o p _.- There are six blanks in total.- Each option supplies exactly six letters to fill the blanks from left to right.- We expect the final completed string to show a neat repetition of a fixed letter block.

Concept / Approach:
The usual pattern in such questions is that the final series becomes a repetition of a short word or block of letters. We can test each option by inserting its letters into the blanks and then checking whether the resulting series can be split into equal sized, identical segments. The option that produces a perfectly repeating pattern is the correct answer.

Step-by-Step Solution:
- Represent the pattern with underscores for blanks: _ o p _ m o _ n _ _ p n m o p _.- Insert the letters of option a: m n p m o n into the blanks, in order.- The resulting complete series is: m o p n m o p n m o p n m o p n.- Now group this string into blocks of four letters: (m o p n), (m o p n), (m o p n), (m o p n).- Each block is exactly the same, showing a clean repetition of the block mopn.

Verification / Alternative check:
- Test option b: filling with m p n m o p does not yield a series that breaks into identical fixed blocks.- Similarly, filling with options c or d results in strings where at least one four letter group differs from the others.- Only option a gives a continuous mopn mopn mopn mopn structure, confirming that mnpmon is the correct sequence to insert.

Why Other Options Are Wrong:
- Options b, c and d cannot be split into repeating identical blocks after substitution, so they fail the standard expectation of a repeated letter pattern.- Option e is not consistent with the required mapping of each blank and also breaks the repetition.

Common Pitfalls:
- Trying to reason letter by letter without checking for a repeating block can make the pattern seem more complex than it is.- Misplacing letters from an option or inserting them in the wrong order can lead to incorrect rejection of the correct alternative.- Not grouping the completed series into equal segments hides the repetitive structure.

Final Answer:
Substituting the letters m n p m o n (option a) produces the perfectly repeating pattern mopn, so the correct sequence to fill the blanks is mnpmon.